// SPDX-License-Identifier: GPL-2.0
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/*
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* Generic ring buffer
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*
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* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
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*/
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#include <linux/trace_events.h>
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#include <linux/ring_buffer.h>
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#include <linux/trace_clock.h>
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#include <linux/sched/clock.h>
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#include <linux/trace_seq.h>
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#include <linux/spinlock.h>
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#include <linux/irq_work.h>
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#include <linux/security.h>
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#include <linux/uaccess.h>
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#include <linux/hardirq.h>
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#include <linux/kthread.h> /* for self test */
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#include <linux/module.h>
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#include <linux/percpu.h>
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#include <linux/mutex.h>
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#include <linux/delay.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/hash.h>
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#include <linux/list.h>
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#include <linux/cpu.h>
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#include <linux/oom.h>
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#include <asm/local.h>
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static void update_pages_handler(struct work_struct *work);
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/*
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* The ring buffer header is special. We must manually up keep it.
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*/
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int ring_buffer_print_entry_header(struct trace_seq *s)
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{
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trace_seq_puts(s, "# compressed entry header\n");
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trace_seq_puts(s, "\ttype_len : 5 bits\n");
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trace_seq_puts(s, "\ttime_delta : 27 bits\n");
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trace_seq_puts(s, "\tarray : 32 bits\n");
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trace_seq_putc(s, '\n');
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trace_seq_printf(s, "\tpadding : type == %d\n",
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RINGBUF_TYPE_PADDING);
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trace_seq_printf(s, "\ttime_extend : type == %d\n",
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RINGBUF_TYPE_TIME_EXTEND);
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trace_seq_printf(s, "\ttime_stamp : type == %d\n",
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RINGBUF_TYPE_TIME_STAMP);
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trace_seq_printf(s, "\tdata max type_len == %d\n",
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RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
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return !trace_seq_has_overflowed(s);
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}
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/*
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* The ring buffer is made up of a list of pages. A separate list of pages is
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* allocated for each CPU. A writer may only write to a buffer that is
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* associated with the CPU it is currently executing on. A reader may read
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* from any per cpu buffer.
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*
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* The reader is special. For each per cpu buffer, the reader has its own
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* reader page. When a reader has read the entire reader page, this reader
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* page is swapped with another page in the ring buffer.
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*
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* Now, as long as the writer is off the reader page, the reader can do what
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* ever it wants with that page. The writer will never write to that page
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* again (as long as it is out of the ring buffer).
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*
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* Here's some silly ASCII art.
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*
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* +------+
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* |reader| RING BUFFER
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* |page |
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* +------+ +---+ +---+ +---+
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* | |-->| |-->| |
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* +---+ +---+ +---+
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* ^ |
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* | |
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* +---------------+
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*
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*
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* +------+
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* |reader| RING BUFFER
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* |page |------------------v
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* +------+ +---+ +---+ +---+
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* | |-->| |-->| |
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* +---+ +---+ +---+
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* ^ |
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* | |
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* +---------------+
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*
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*
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* +------+
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* |reader| RING BUFFER
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* |page |------------------v
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* +------+ +---+ +---+ +---+
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* ^ | |-->| |-->| |
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* | +---+ +---+ +---+
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* | |
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* | |
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* +------------------------------+
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*
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*
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* +------+
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* |buffer| RING BUFFER
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* |page |------------------v
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* +------+ +---+ +---+ +---+
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* ^ | | | |-->| |
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* | New +---+ +---+ +---+
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* | Reader------^ |
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* | page |
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* +------------------------------+
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*
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*
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* After we make this swap, the reader can hand this page off to the splice
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* code and be done with it. It can even allocate a new page if it needs to
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* and swap that into the ring buffer.
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*
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* We will be using cmpxchg soon to make all this lockless.
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*
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*/
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/* Used for individual buffers (after the counter) */
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#define RB_BUFFER_OFF (1 << 20)
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#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
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#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
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#define RB_ALIGNMENT 4U
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#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
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#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
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#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
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# define RB_FORCE_8BYTE_ALIGNMENT 0
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# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
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#else
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# define RB_FORCE_8BYTE_ALIGNMENT 1
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# define RB_ARCH_ALIGNMENT 8U
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#endif
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#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
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/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
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#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
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enum {
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RB_LEN_TIME_EXTEND = 8,
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RB_LEN_TIME_STAMP = 8,
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};
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#define skip_time_extend(event) \
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((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
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#define extended_time(event) \
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(event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
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static inline int rb_null_event(struct ring_buffer_event *event)
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{
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return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
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}
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static void rb_event_set_padding(struct ring_buffer_event *event)
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{
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/* padding has a NULL time_delta */
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event->type_len = RINGBUF_TYPE_PADDING;
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event->time_delta = 0;
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}
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static unsigned
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rb_event_data_length(struct ring_buffer_event *event)
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{
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unsigned length;
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if (event->type_len)
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length = event->type_len * RB_ALIGNMENT;
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else
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length = event->array[0];
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return length + RB_EVNT_HDR_SIZE;
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}
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/*
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* Return the length of the given event. Will return
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* the length of the time extend if the event is a
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* time extend.
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*/
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static inline unsigned
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rb_event_length(struct ring_buffer_event *event)
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{
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switch (event->type_len) {
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case RINGBUF_TYPE_PADDING:
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if (rb_null_event(event))
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/* undefined */
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return -1;
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return event->array[0] + RB_EVNT_HDR_SIZE;
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case RINGBUF_TYPE_TIME_EXTEND:
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return RB_LEN_TIME_EXTEND;
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case RINGBUF_TYPE_TIME_STAMP:
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return RB_LEN_TIME_STAMP;
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case RINGBUF_TYPE_DATA:
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return rb_event_data_length(event);
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default:
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WARN_ON_ONCE(1);
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}
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/* not hit */
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return 0;
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}
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/*
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* Return total length of time extend and data,
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* or just the event length for all other events.
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*/
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static inline unsigned
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rb_event_ts_length(struct ring_buffer_event *event)
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{
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unsigned len = 0;
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if (extended_time(event)) {
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/* time extends include the data event after it */
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len = RB_LEN_TIME_EXTEND;
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event = skip_time_extend(event);
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}
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return len + rb_event_length(event);
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}
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/**
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* ring_buffer_event_length - return the length of the event
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* @event: the event to get the length of
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*
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* Returns the size of the data load of a data event.
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* If the event is something other than a data event, it
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* returns the size of the event itself. With the exception
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* of a TIME EXTEND, where it still returns the size of the
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* data load of the data event after it.
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*/
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unsigned ring_buffer_event_length(struct ring_buffer_event *event)
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{
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unsigned length;
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if (extended_time(event))
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event = skip_time_extend(event);
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length = rb_event_length(event);
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if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
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return length;
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length -= RB_EVNT_HDR_SIZE;
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if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
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length -= sizeof(event->array[0]);
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return length;
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}
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EXPORT_SYMBOL_GPL(ring_buffer_event_length);
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/* inline for ring buffer fast paths */
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static __always_inline void *
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rb_event_data(struct ring_buffer_event *event)
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{
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if (extended_time(event))
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event = skip_time_extend(event);
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WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
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/* If length is in len field, then array[0] has the data */
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if (event->type_len)
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return (void *)&event->array[0];
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/* Otherwise length is in array[0] and array[1] has the data */
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return (void *)&event->array[1];
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}
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/**
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* ring_buffer_event_data - return the data of the event
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* @event: the event to get the data from
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*/
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void *ring_buffer_event_data(struct ring_buffer_event *event)
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{
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return rb_event_data(event);
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}
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EXPORT_SYMBOL_GPL(ring_buffer_event_data);
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#define for_each_buffer_cpu(buffer, cpu) \
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for_each_cpu(cpu, buffer->cpumask)
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#define for_each_online_buffer_cpu(buffer, cpu) \
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for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
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#define TS_SHIFT 27
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#define TS_MASK ((1ULL << TS_SHIFT) - 1)
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#define TS_DELTA_TEST (~TS_MASK)
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/**
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* ring_buffer_event_time_stamp - return the event's extended timestamp
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* @event: the event to get the timestamp of
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*
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* Returns the extended timestamp associated with a data event.
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* An extended time_stamp is a 64-bit timestamp represented
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* internally in a special way that makes the best use of space
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* contained within a ring buffer event. This function decodes
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* it and maps it to a straight u64 value.
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*/
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u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event)
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{
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u64 ts;
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ts = event->array[0];
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ts <<= TS_SHIFT;
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ts += event->time_delta;
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return ts;
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}
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/* Flag when events were overwritten */
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#define RB_MISSED_EVENTS (1 << 31)
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/* Missed count stored at end */
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#define RB_MISSED_STORED (1 << 30)
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struct buffer_data_page {
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u64 time_stamp; /* page time stamp */
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local_t commit; /* write committed index */
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unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
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};
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/*
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* Note, the buffer_page list must be first. The buffer pages
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* are allocated in cache lines, which means that each buffer
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* page will be at the beginning of a cache line, and thus
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* the least significant bits will be zero. We use this to
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* add flags in the list struct pointers, to make the ring buffer
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* lockless.
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*/
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struct buffer_page {
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struct list_head list; /* list of buffer pages */
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local_t write; /* index for next write */
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unsigned read; /* index for next read */
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local_t entries; /* entries on this page */
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unsigned long real_end; /* real end of data */
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struct buffer_data_page *page; /* Actual data page */
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};
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/*
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* The buffer page counters, write and entries, must be reset
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* atomically when crossing page boundaries. To synchronize this
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* update, two counters are inserted into the number. One is
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* the actual counter for the write position or count on the page.
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*
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* The other is a counter of updaters. Before an update happens
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* the update partition of the counter is incremented. This will
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* allow the updater to update the counter atomically.
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*
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* The counter is 20 bits, and the state data is 12.
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*/
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#define RB_WRITE_MASK 0xfffff
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#define RB_WRITE_INTCNT (1 << 20)
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static void rb_init_page(struct buffer_data_page *bpage)
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{
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local_set(&bpage->commit, 0);
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}
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/*
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* Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
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* this issue out.
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*/
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static void free_buffer_page(struct buffer_page *bpage)
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{
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free_page((unsigned long)bpage->page);
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kfree(bpage);
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}
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/*
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* We need to fit the time_stamp delta into 27 bits.
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*/
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static inline int test_time_stamp(u64 delta)
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{
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if (delta & TS_DELTA_TEST)
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return 1;
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return 0;
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}
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#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
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/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
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#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
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int ring_buffer_print_page_header(struct trace_seq *s)
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{
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struct buffer_data_page field;
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trace_seq_printf(s, "\tfield: u64 timestamp;\t"
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"offset:0;\tsize:%u;\tsigned:%u;\n",
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(unsigned int)sizeof(field.time_stamp),
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(unsigned int)is_signed_type(u64));
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trace_seq_printf(s, "\tfield: local_t commit;\t"
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"offset:%u;\tsize:%u;\tsigned:%u;\n",
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(unsigned int)offsetof(typeof(field), commit),
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(unsigned int)sizeof(field.commit),
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(unsigned int)is_signed_type(long));
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trace_seq_printf(s, "\tfield: int overwrite;\t"
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"offset:%u;\tsize:%u;\tsigned:%u;\n",
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(unsigned int)offsetof(typeof(field), commit),
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1,
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(unsigned int)is_signed_type(long));
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trace_seq_printf(s, "\tfield: char data;\t"
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"offset:%u;\tsize:%u;\tsigned:%u;\n",
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(unsigned int)offsetof(typeof(field), data),
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(unsigned int)BUF_PAGE_SIZE,
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(unsigned int)is_signed_type(char));
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return !trace_seq_has_overflowed(s);
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}
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struct rb_irq_work {
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struct irq_work work;
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wait_queue_head_t waiters;
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wait_queue_head_t full_waiters;
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long wait_index;
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bool waiters_pending;
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bool full_waiters_pending;
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bool wakeup_full;
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};
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/*
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* Structure to hold event state and handle nested events.
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*/
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struct rb_event_info {
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u64 ts;
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u64 delta;
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u64 before;
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u64 after;
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unsigned long length;
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struct buffer_page *tail_page;
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int add_timestamp;
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};
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/*
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* Used for the add_timestamp
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* NONE
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* EXTEND - wants a time extend
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* ABSOLUTE - the buffer requests all events to have absolute time stamps
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* FORCE - force a full time stamp.
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*/
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enum {
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RB_ADD_STAMP_NONE = 0,
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RB_ADD_STAMP_EXTEND = BIT(1),
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RB_ADD_STAMP_ABSOLUTE = BIT(2),
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RB_ADD_STAMP_FORCE = BIT(3)
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};
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/*
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* Used for which event context the event is in.
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* TRANSITION = 0
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* NMI = 1
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* IRQ = 2
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* SOFTIRQ = 3
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* NORMAL = 4
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*
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* See trace_recursive_lock() comment below for more details.
|
*/
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enum {
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RB_CTX_TRANSITION,
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RB_CTX_NMI,
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RB_CTX_IRQ,
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RB_CTX_SOFTIRQ,
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RB_CTX_NORMAL,
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RB_CTX_MAX
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};
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#if BITS_PER_LONG == 32
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#define RB_TIME_32
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#endif
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/* To test on 64 bit machines */
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//#define RB_TIME_32
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#ifdef RB_TIME_32
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struct rb_time_struct {
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local_t cnt;
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local_t top;
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local_t bottom;
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};
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#else
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#include <asm/local64.h>
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struct rb_time_struct {
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local64_t time;
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};
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#endif
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typedef struct rb_time_struct rb_time_t;
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/*
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* head_page == tail_page && head == tail then buffer is empty.
|
*/
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struct ring_buffer_per_cpu {
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int cpu;
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atomic_t record_disabled;
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atomic_t resize_disabled;
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struct trace_buffer *buffer;
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raw_spinlock_t reader_lock; /* serialize readers */
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arch_spinlock_t lock;
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struct lock_class_key lock_key;
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struct buffer_data_page *free_page;
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unsigned long nr_pages;
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unsigned int current_context;
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struct list_head *pages;
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struct buffer_page *head_page; /* read from head */
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struct buffer_page *tail_page; /* write to tail */
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struct buffer_page *commit_page; /* committed pages */
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struct buffer_page *reader_page;
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unsigned long lost_events;
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unsigned long last_overrun;
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unsigned long nest;
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local_t entries_bytes;
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local_t entries;
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local_t overrun;
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local_t commit_overrun;
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local_t dropped_events;
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local_t committing;
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local_t commits;
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local_t pages_touched;
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local_t pages_lost;
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local_t pages_read;
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long last_pages_touch;
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size_t shortest_full;
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unsigned long read;
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unsigned long read_bytes;
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rb_time_t write_stamp;
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rb_time_t before_stamp;
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u64 read_stamp;
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/* ring buffer pages to update, > 0 to add, < 0 to remove */
|
long nr_pages_to_update;
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struct list_head new_pages; /* new pages to add */
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struct work_struct update_pages_work;
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struct completion update_done;
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struct rb_irq_work irq_work;
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};
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struct trace_buffer {
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unsigned flags;
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int cpus;
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atomic_t record_disabled;
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cpumask_var_t cpumask;
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|
struct lock_class_key *reader_lock_key;
|
|
struct mutex mutex;
|
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struct ring_buffer_per_cpu **buffers;
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struct hlist_node node;
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u64 (*clock)(void);
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struct rb_irq_work irq_work;
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bool time_stamp_abs;
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};
|
|
struct ring_buffer_iter {
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struct ring_buffer_per_cpu *cpu_buffer;
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unsigned long head;
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unsigned long next_event;
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struct buffer_page *head_page;
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struct buffer_page *cache_reader_page;
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unsigned long cache_read;
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u64 read_stamp;
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u64 page_stamp;
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struct ring_buffer_event *event;
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int missed_events;
|
};
|
|
#ifdef RB_TIME_32
|
|
/*
|
* On 32 bit machines, local64_t is very expensive. As the ring
|
* buffer doesn't need all the features of a true 64 bit atomic,
|
* on 32 bit, it uses these functions (64 still uses local64_t).
|
*
|
* For the ring buffer, 64 bit required operations for the time is
|
* the following:
|
*
|
* - Only need 59 bits (uses 60 to make it even).
|
* - Reads may fail if it interrupted a modification of the time stamp.
|
* It will succeed if it did not interrupt another write even if
|
* the read itself is interrupted by a write.
|
* It returns whether it was successful or not.
|
*
|
* - Writes always succeed and will overwrite other writes and writes
|
* that were done by events interrupting the current write.
|
*
|
* - A write followed by a read of the same time stamp will always succeed,
|
* but may not contain the same value.
|
*
|
* - A cmpxchg will fail if it interrupted another write or cmpxchg.
|
* Other than that, it acts like a normal cmpxchg.
|
*
|
* The 60 bit time stamp is broken up by 30 bits in a top and bottom half
|
* (bottom being the least significant 30 bits of the 60 bit time stamp).
|
*
|
* The two most significant bits of each half holds a 2 bit counter (0-3).
|
* Each update will increment this counter by one.
|
* When reading the top and bottom, if the two counter bits match then the
|
* top and bottom together make a valid 60 bit number.
|
*/
|
#define RB_TIME_SHIFT 30
|
#define RB_TIME_VAL_MASK ((1 << RB_TIME_SHIFT) - 1)
|
|
static inline int rb_time_cnt(unsigned long val)
|
{
|
return (val >> RB_TIME_SHIFT) & 3;
|
}
|
|
static inline u64 rb_time_val(unsigned long top, unsigned long bottom)
|
{
|
u64 val;
|
|
val = top & RB_TIME_VAL_MASK;
|
val <<= RB_TIME_SHIFT;
|
val |= bottom & RB_TIME_VAL_MASK;
|
|
return val;
|
}
|
|
static inline bool __rb_time_read(rb_time_t *t, u64 *ret, unsigned long *cnt)
|
{
|
unsigned long top, bottom;
|
unsigned long c;
|
|
/*
|
* If the read is interrupted by a write, then the cnt will
|
* be different. Loop until both top and bottom have been read
|
* without interruption.
|
*/
|
do {
|
c = local_read(&t->cnt);
|
top = local_read(&t->top);
|
bottom = local_read(&t->bottom);
|
} while (c != local_read(&t->cnt));
|
|
*cnt = rb_time_cnt(top);
|
|
/* If top and bottom counts don't match, this interrupted a write */
|
if (*cnt != rb_time_cnt(bottom))
|
return false;
|
|
*ret = rb_time_val(top, bottom);
|
return true;
|
}
|
|
static bool rb_time_read(rb_time_t *t, u64 *ret)
|
{
|
unsigned long cnt;
|
|
return __rb_time_read(t, ret, &cnt);
|
}
|
|
static inline unsigned long rb_time_val_cnt(unsigned long val, unsigned long cnt)
|
{
|
return (val & RB_TIME_VAL_MASK) | ((cnt & 3) << RB_TIME_SHIFT);
|
}
|
|
static inline void rb_time_split(u64 val, unsigned long *top, unsigned long *bottom)
|
{
|
*top = (unsigned long)((val >> RB_TIME_SHIFT) & RB_TIME_VAL_MASK);
|
*bottom = (unsigned long)(val & RB_TIME_VAL_MASK);
|
}
|
|
static inline void rb_time_val_set(local_t *t, unsigned long val, unsigned long cnt)
|
{
|
val = rb_time_val_cnt(val, cnt);
|
local_set(t, val);
|
}
|
|
static void rb_time_set(rb_time_t *t, u64 val)
|
{
|
unsigned long cnt, top, bottom;
|
|
rb_time_split(val, &top, &bottom);
|
|
/* Writes always succeed with a valid number even if it gets interrupted. */
|
do {
|
cnt = local_inc_return(&t->cnt);
|
rb_time_val_set(&t->top, top, cnt);
|
rb_time_val_set(&t->bottom, bottom, cnt);
|
} while (cnt != local_read(&t->cnt));
|
}
|
|
static inline bool
|
rb_time_read_cmpxchg(local_t *l, unsigned long expect, unsigned long set)
|
{
|
unsigned long ret;
|
|
ret = local_cmpxchg(l, expect, set);
|
return ret == expect;
|
}
|
|
static int rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
|
{
|
unsigned long cnt, top, bottom;
|
unsigned long cnt2, top2, bottom2;
|
u64 val;
|
|
/* The cmpxchg always fails if it interrupted an update */
|
if (!__rb_time_read(t, &val, &cnt2))
|
return false;
|
|
if (val != expect)
|
return false;
|
|
cnt = local_read(&t->cnt);
|
if ((cnt & 3) != cnt2)
|
return false;
|
|
cnt2 = cnt + 1;
|
|
rb_time_split(val, &top, &bottom);
|
top = rb_time_val_cnt(top, cnt);
|
bottom = rb_time_val_cnt(bottom, cnt);
|
|
rb_time_split(set, &top2, &bottom2);
|
top2 = rb_time_val_cnt(top2, cnt2);
|
bottom2 = rb_time_val_cnt(bottom2, cnt2);
|
|
if (!rb_time_read_cmpxchg(&t->cnt, cnt, cnt2))
|
return false;
|
if (!rb_time_read_cmpxchg(&t->top, top, top2))
|
return false;
|
if (!rb_time_read_cmpxchg(&t->bottom, bottom, bottom2))
|
return false;
|
return true;
|
}
|
|
#else /* 64 bits */
|
|
/* local64_t always succeeds */
|
|
static inline bool rb_time_read(rb_time_t *t, u64 *ret)
|
{
|
*ret = local64_read(&t->time);
|
return true;
|
}
|
static void rb_time_set(rb_time_t *t, u64 val)
|
{
|
local64_set(&t->time, val);
|
}
|
|
static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
|
{
|
u64 val;
|
val = local64_cmpxchg(&t->time, expect, set);
|
return val == expect;
|
}
|
#endif
|
|
/**
|
* ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
|
* @buffer: The ring_buffer to get the number of pages from
|
* @cpu: The cpu of the ring_buffer to get the number of pages from
|
*
|
* Returns the number of pages used by a per_cpu buffer of the ring buffer.
|
*/
|
size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
|
{
|
return buffer->buffers[cpu]->nr_pages;
|
}
|
|
/**
|
* ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer
|
* @buffer: The ring_buffer to get the number of pages from
|
* @cpu: The cpu of the ring_buffer to get the number of pages from
|
*
|
* Returns the number of pages that have content in the ring buffer.
|
*/
|
size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
|
{
|
size_t read;
|
size_t lost;
|
size_t cnt;
|
|
read = local_read(&buffer->buffers[cpu]->pages_read);
|
lost = local_read(&buffer->buffers[cpu]->pages_lost);
|
cnt = local_read(&buffer->buffers[cpu]->pages_touched);
|
|
if (WARN_ON_ONCE(cnt < lost))
|
return 0;
|
|
cnt -= lost;
|
|
/* The reader can read an empty page, but not more than that */
|
if (cnt < read) {
|
WARN_ON_ONCE(read > cnt + 1);
|
return 0;
|
}
|
|
return cnt - read;
|
}
|
|
static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
size_t nr_pages;
|
size_t dirty;
|
|
nr_pages = cpu_buffer->nr_pages;
|
if (!nr_pages || !full)
|
return true;
|
|
dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
|
|
return (dirty * 100) > (full * nr_pages);
|
}
|
|
/*
|
* rb_wake_up_waiters - wake up tasks waiting for ring buffer input
|
*
|
* Schedules a delayed work to wake up any task that is blocked on the
|
* ring buffer waiters queue.
|
*/
|
static void rb_wake_up_waiters(struct irq_work *work)
|
{
|
struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
|
|
wake_up_all(&rbwork->waiters);
|
if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
|
rbwork->wakeup_full = false;
|
rbwork->full_waiters_pending = false;
|
wake_up_all(&rbwork->full_waiters);
|
}
|
}
|
|
/**
|
* ring_buffer_wake_waiters - wake up any waiters on this ring buffer
|
* @buffer: The ring buffer to wake waiters on
|
*
|
* In the case of a file that represents a ring buffer is closing,
|
* it is prudent to wake up any waiters that are on this.
|
*/
|
void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
struct rb_irq_work *rbwork;
|
|
if (cpu == RING_BUFFER_ALL_CPUS) {
|
|
/* Wake up individual ones too. One level recursion */
|
for_each_buffer_cpu(buffer, cpu)
|
ring_buffer_wake_waiters(buffer, cpu);
|
|
rbwork = &buffer->irq_work;
|
} else {
|
cpu_buffer = buffer->buffers[cpu];
|
rbwork = &cpu_buffer->irq_work;
|
}
|
|
rbwork->wait_index++;
|
/* make sure the waiters see the new index */
|
smp_wmb();
|
|
rb_wake_up_waiters(&rbwork->work);
|
}
|
|
/**
|
* ring_buffer_wait - wait for input to the ring buffer
|
* @buffer: buffer to wait on
|
* @cpu: the cpu buffer to wait on
|
* @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
|
*
|
* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
|
* as data is added to any of the @buffer's cpu buffers. Otherwise
|
* it will wait for data to be added to a specific cpu buffer.
|
*/
|
int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
DEFINE_WAIT(wait);
|
struct rb_irq_work *work;
|
long wait_index;
|
int ret = 0;
|
|
/*
|
* Depending on what the caller is waiting for, either any
|
* data in any cpu buffer, or a specific buffer, put the
|
* caller on the appropriate wait queue.
|
*/
|
if (cpu == RING_BUFFER_ALL_CPUS) {
|
work = &buffer->irq_work;
|
/* Full only makes sense on per cpu reads */
|
full = 0;
|
} else {
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return -ENODEV;
|
cpu_buffer = buffer->buffers[cpu];
|
work = &cpu_buffer->irq_work;
|
}
|
|
wait_index = READ_ONCE(work->wait_index);
|
|
while (true) {
|
if (full)
|
prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
|
else
|
prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
|
|
/*
|
* The events can happen in critical sections where
|
* checking a work queue can cause deadlocks.
|
* After adding a task to the queue, this flag is set
|
* only to notify events to try to wake up the queue
|
* using irq_work.
|
*
|
* We don't clear it even if the buffer is no longer
|
* empty. The flag only causes the next event to run
|
* irq_work to do the work queue wake up. The worse
|
* that can happen if we race with !trace_empty() is that
|
* an event will cause an irq_work to try to wake up
|
* an empty queue.
|
*
|
* There's no reason to protect this flag either, as
|
* the work queue and irq_work logic will do the necessary
|
* synchronization for the wake ups. The only thing
|
* that is necessary is that the wake up happens after
|
* a task has been queued. It's OK for spurious wake ups.
|
*/
|
if (full)
|
work->full_waiters_pending = true;
|
else
|
work->waiters_pending = true;
|
|
if (signal_pending(current)) {
|
ret = -EINTR;
|
break;
|
}
|
|
if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
|
break;
|
|
if (cpu != RING_BUFFER_ALL_CPUS &&
|
!ring_buffer_empty_cpu(buffer, cpu)) {
|
unsigned long flags;
|
bool pagebusy;
|
bool done;
|
|
if (!full)
|
break;
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
|
done = !pagebusy && full_hit(buffer, cpu, full);
|
|
if (!cpu_buffer->shortest_full ||
|
cpu_buffer->shortest_full > full)
|
cpu_buffer->shortest_full = full;
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
if (done)
|
break;
|
}
|
|
schedule();
|
|
/* Make sure to see the new wait index */
|
smp_rmb();
|
if (wait_index != work->wait_index)
|
break;
|
}
|
|
if (full)
|
finish_wait(&work->full_waiters, &wait);
|
else
|
finish_wait(&work->waiters, &wait);
|
|
return ret;
|
}
|
|
/**
|
* ring_buffer_poll_wait - poll on buffer input
|
* @buffer: buffer to wait on
|
* @cpu: the cpu buffer to wait on
|
* @filp: the file descriptor
|
* @poll_table: The poll descriptor
|
* @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
|
*
|
* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
|
* as data is added to any of the @buffer's cpu buffers. Otherwise
|
* it will wait for data to be added to a specific cpu buffer.
|
*
|
* Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
|
* zero otherwise.
|
*/
|
__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
|
struct file *filp, poll_table *poll_table, int full)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
struct rb_irq_work *work;
|
|
if (cpu == RING_BUFFER_ALL_CPUS) {
|
work = &buffer->irq_work;
|
full = 0;
|
} else {
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return -EINVAL;
|
|
cpu_buffer = buffer->buffers[cpu];
|
work = &cpu_buffer->irq_work;
|
}
|
|
if (full) {
|
poll_wait(filp, &work->full_waiters, poll_table);
|
work->full_waiters_pending = true;
|
} else {
|
poll_wait(filp, &work->waiters, poll_table);
|
work->waiters_pending = true;
|
}
|
|
/*
|
* There's a tight race between setting the waiters_pending and
|
* checking if the ring buffer is empty. Once the waiters_pending bit
|
* is set, the next event will wake the task up, but we can get stuck
|
* if there's only a single event in.
|
*
|
* FIXME: Ideally, we need a memory barrier on the writer side as well,
|
* but adding a memory barrier to all events will cause too much of a
|
* performance hit in the fast path. We only need a memory barrier when
|
* the buffer goes from empty to having content. But as this race is
|
* extremely small, and it's not a problem if another event comes in, we
|
* will fix it later.
|
*/
|
smp_mb();
|
|
if (full)
|
return full_hit(buffer, cpu, full) ? EPOLLIN | EPOLLRDNORM : 0;
|
|
if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
|
(cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
|
return EPOLLIN | EPOLLRDNORM;
|
return 0;
|
}
|
|
/* buffer may be either ring_buffer or ring_buffer_per_cpu */
|
#define RB_WARN_ON(b, cond) \
|
({ \
|
int _____ret = unlikely(cond); \
|
if (_____ret) { \
|
if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
|
struct ring_buffer_per_cpu *__b = \
|
(void *)b; \
|
atomic_inc(&__b->buffer->record_disabled); \
|
} else \
|
atomic_inc(&b->record_disabled); \
|
WARN_ON(1); \
|
} \
|
_____ret; \
|
})
|
|
/* Up this if you want to test the TIME_EXTENTS and normalization */
|
#define DEBUG_SHIFT 0
|
|
static inline u64 rb_time_stamp(struct trace_buffer *buffer)
|
{
|
u64 ts;
|
|
/* Skip retpolines :-( */
|
if (IS_ENABLED(CONFIG_RETPOLINE) && likely(buffer->clock == trace_clock_local))
|
ts = trace_clock_local();
|
else
|
ts = buffer->clock();
|
|
/* shift to debug/test normalization and TIME_EXTENTS */
|
return ts << DEBUG_SHIFT;
|
}
|
|
u64 ring_buffer_time_stamp(struct trace_buffer *buffer, int cpu)
|
{
|
u64 time;
|
|
preempt_disable_notrace();
|
time = rb_time_stamp(buffer);
|
preempt_enable_notrace();
|
|
return time;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
|
|
void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
|
int cpu, u64 *ts)
|
{
|
/* Just stupid testing the normalize function and deltas */
|
*ts >>= DEBUG_SHIFT;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
|
|
/*
|
* Making the ring buffer lockless makes things tricky.
|
* Although writes only happen on the CPU that they are on,
|
* and they only need to worry about interrupts. Reads can
|
* happen on any CPU.
|
*
|
* The reader page is always off the ring buffer, but when the
|
* reader finishes with a page, it needs to swap its page with
|
* a new one from the buffer. The reader needs to take from
|
* the head (writes go to the tail). But if a writer is in overwrite
|
* mode and wraps, it must push the head page forward.
|
*
|
* Here lies the problem.
|
*
|
* The reader must be careful to replace only the head page, and
|
* not another one. As described at the top of the file in the
|
* ASCII art, the reader sets its old page to point to the next
|
* page after head. It then sets the page after head to point to
|
* the old reader page. But if the writer moves the head page
|
* during this operation, the reader could end up with the tail.
|
*
|
* We use cmpxchg to help prevent this race. We also do something
|
* special with the page before head. We set the LSB to 1.
|
*
|
* When the writer must push the page forward, it will clear the
|
* bit that points to the head page, move the head, and then set
|
* the bit that points to the new head page.
|
*
|
* We also don't want an interrupt coming in and moving the head
|
* page on another writer. Thus we use the second LSB to catch
|
* that too. Thus:
|
*
|
* head->list->prev->next bit 1 bit 0
|
* ------- -------
|
* Normal page 0 0
|
* Points to head page 0 1
|
* New head page 1 0
|
*
|
* Note we can not trust the prev pointer of the head page, because:
|
*
|
* +----+ +-----+ +-----+
|
* | |------>| T |---X--->| N |
|
* | |<------| | | |
|
* +----+ +-----+ +-----+
|
* ^ ^ |
|
* | +-----+ | |
|
* +----------| R |----------+ |
|
* | |<-----------+
|
* +-----+
|
*
|
* Key: ---X--> HEAD flag set in pointer
|
* T Tail page
|
* R Reader page
|
* N Next page
|
*
|
* (see __rb_reserve_next() to see where this happens)
|
*
|
* What the above shows is that the reader just swapped out
|
* the reader page with a page in the buffer, but before it
|
* could make the new header point back to the new page added
|
* it was preempted by a writer. The writer moved forward onto
|
* the new page added by the reader and is about to move forward
|
* again.
|
*
|
* You can see, it is legitimate for the previous pointer of
|
* the head (or any page) not to point back to itself. But only
|
* temporarily.
|
*/
|
|
#define RB_PAGE_NORMAL 0UL
|
#define RB_PAGE_HEAD 1UL
|
#define RB_PAGE_UPDATE 2UL
|
|
|
#define RB_FLAG_MASK 3UL
|
|
/* PAGE_MOVED is not part of the mask */
|
#define RB_PAGE_MOVED 4UL
|
|
/*
|
* rb_list_head - remove any bit
|
*/
|
static struct list_head *rb_list_head(struct list_head *list)
|
{
|
unsigned long val = (unsigned long)list;
|
|
return (struct list_head *)(val & ~RB_FLAG_MASK);
|
}
|
|
/*
|
* rb_is_head_page - test if the given page is the head page
|
*
|
* Because the reader may move the head_page pointer, we can
|
* not trust what the head page is (it may be pointing to
|
* the reader page). But if the next page is a header page,
|
* its flags will be non zero.
|
*/
|
static inline int
|
rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
|
struct buffer_page *page, struct list_head *list)
|
{
|
unsigned long val;
|
|
val = (unsigned long)list->next;
|
|
if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
|
return RB_PAGE_MOVED;
|
|
return val & RB_FLAG_MASK;
|
}
|
|
/*
|
* rb_is_reader_page
|
*
|
* The unique thing about the reader page, is that, if the
|
* writer is ever on it, the previous pointer never points
|
* back to the reader page.
|
*/
|
static bool rb_is_reader_page(struct buffer_page *page)
|
{
|
struct list_head *list = page->list.prev;
|
|
return rb_list_head(list->next) != &page->list;
|
}
|
|
/*
|
* rb_set_list_to_head - set a list_head to be pointing to head.
|
*/
|
static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
|
struct list_head *list)
|
{
|
unsigned long *ptr;
|
|
ptr = (unsigned long *)&list->next;
|
*ptr |= RB_PAGE_HEAD;
|
*ptr &= ~RB_PAGE_UPDATE;
|
}
|
|
/*
|
* rb_head_page_activate - sets up head page
|
*/
|
static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
struct buffer_page *head;
|
|
head = cpu_buffer->head_page;
|
if (!head)
|
return;
|
|
/*
|
* Set the previous list pointer to have the HEAD flag.
|
*/
|
rb_set_list_to_head(cpu_buffer, head->list.prev);
|
}
|
|
static void rb_list_head_clear(struct list_head *list)
|
{
|
unsigned long *ptr = (unsigned long *)&list->next;
|
|
*ptr &= ~RB_FLAG_MASK;
|
}
|
|
/*
|
* rb_head_page_deactivate - clears head page ptr (for free list)
|
*/
|
static void
|
rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
struct list_head *hd;
|
|
/* Go through the whole list and clear any pointers found. */
|
rb_list_head_clear(cpu_buffer->pages);
|
|
list_for_each(hd, cpu_buffer->pages)
|
rb_list_head_clear(hd);
|
}
|
|
static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
|
struct buffer_page *head,
|
struct buffer_page *prev,
|
int old_flag, int new_flag)
|
{
|
struct list_head *list;
|
unsigned long val = (unsigned long)&head->list;
|
unsigned long ret;
|
|
list = &prev->list;
|
|
val &= ~RB_FLAG_MASK;
|
|
ret = cmpxchg((unsigned long *)&list->next,
|
val | old_flag, val | new_flag);
|
|
/* check if the reader took the page */
|
if ((ret & ~RB_FLAG_MASK) != val)
|
return RB_PAGE_MOVED;
|
|
return ret & RB_FLAG_MASK;
|
}
|
|
static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
|
struct buffer_page *head,
|
struct buffer_page *prev,
|
int old_flag)
|
{
|
return rb_head_page_set(cpu_buffer, head, prev,
|
old_flag, RB_PAGE_UPDATE);
|
}
|
|
static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
|
struct buffer_page *head,
|
struct buffer_page *prev,
|
int old_flag)
|
{
|
return rb_head_page_set(cpu_buffer, head, prev,
|
old_flag, RB_PAGE_HEAD);
|
}
|
|
static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
|
struct buffer_page *head,
|
struct buffer_page *prev,
|
int old_flag)
|
{
|
return rb_head_page_set(cpu_buffer, head, prev,
|
old_flag, RB_PAGE_NORMAL);
|
}
|
|
static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
|
struct buffer_page **bpage)
|
{
|
struct list_head *p = rb_list_head((*bpage)->list.next);
|
|
*bpage = list_entry(p, struct buffer_page, list);
|
}
|
|
static struct buffer_page *
|
rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
struct buffer_page *head;
|
struct buffer_page *page;
|
struct list_head *list;
|
int i;
|
|
if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
|
return NULL;
|
|
/* sanity check */
|
list = cpu_buffer->pages;
|
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
|
return NULL;
|
|
page = head = cpu_buffer->head_page;
|
/*
|
* It is possible that the writer moves the header behind
|
* where we started, and we miss in one loop.
|
* A second loop should grab the header, but we'll do
|
* three loops just because I'm paranoid.
|
*/
|
for (i = 0; i < 3; i++) {
|
do {
|
if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
|
cpu_buffer->head_page = page;
|
return page;
|
}
|
rb_inc_page(cpu_buffer, &page);
|
} while (page != head);
|
}
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
return NULL;
|
}
|
|
static int rb_head_page_replace(struct buffer_page *old,
|
struct buffer_page *new)
|
{
|
unsigned long *ptr = (unsigned long *)&old->list.prev->next;
|
unsigned long val;
|
unsigned long ret;
|
|
val = *ptr & ~RB_FLAG_MASK;
|
val |= RB_PAGE_HEAD;
|
|
ret = cmpxchg(ptr, val, (unsigned long)&new->list);
|
|
return ret == val;
|
}
|
|
/*
|
* rb_tail_page_update - move the tail page forward
|
*/
|
static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
|
struct buffer_page *tail_page,
|
struct buffer_page *next_page)
|
{
|
unsigned long old_entries;
|
unsigned long old_write;
|
|
/*
|
* The tail page now needs to be moved forward.
|
*
|
* We need to reset the tail page, but without messing
|
* with possible erasing of data brought in by interrupts
|
* that have moved the tail page and are currently on it.
|
*
|
* We add a counter to the write field to denote this.
|
*/
|
old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
|
old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
|
|
local_inc(&cpu_buffer->pages_touched);
|
/*
|
* Just make sure we have seen our old_write and synchronize
|
* with any interrupts that come in.
|
*/
|
barrier();
|
|
/*
|
* If the tail page is still the same as what we think
|
* it is, then it is up to us to update the tail
|
* pointer.
|
*/
|
if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
|
/* Zero the write counter */
|
unsigned long val = old_write & ~RB_WRITE_MASK;
|
unsigned long eval = old_entries & ~RB_WRITE_MASK;
|
|
/*
|
* This will only succeed if an interrupt did
|
* not come in and change it. In which case, we
|
* do not want to modify it.
|
*
|
* We add (void) to let the compiler know that we do not care
|
* about the return value of these functions. We use the
|
* cmpxchg to only update if an interrupt did not already
|
* do it for us. If the cmpxchg fails, we don't care.
|
*/
|
(void)local_cmpxchg(&next_page->write, old_write, val);
|
(void)local_cmpxchg(&next_page->entries, old_entries, eval);
|
|
/*
|
* No need to worry about races with clearing out the commit.
|
* it only can increment when a commit takes place. But that
|
* only happens in the outer most nested commit.
|
*/
|
local_set(&next_page->page->commit, 0);
|
|
/* Again, either we update tail_page or an interrupt does */
|
(void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
|
}
|
}
|
|
static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
|
struct buffer_page *bpage)
|
{
|
unsigned long val = (unsigned long)bpage;
|
|
if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
|
return 1;
|
|
return 0;
|
}
|
|
/**
|
* rb_check_list - make sure a pointer to a list has the last bits zero
|
*/
|
static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
|
struct list_head *list)
|
{
|
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
|
return 1;
|
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
|
return 1;
|
return 0;
|
}
|
|
/**
|
* rb_check_pages - integrity check of buffer pages
|
* @cpu_buffer: CPU buffer with pages to test
|
*
|
* As a safety measure we check to make sure the data pages have not
|
* been corrupted.
|
*/
|
static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
struct list_head *head = cpu_buffer->pages;
|
struct buffer_page *bpage, *tmp;
|
|
/* Reset the head page if it exists */
|
if (cpu_buffer->head_page)
|
rb_set_head_page(cpu_buffer);
|
|
rb_head_page_deactivate(cpu_buffer);
|
|
if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
|
return -1;
|
if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
|
return -1;
|
|
if (rb_check_list(cpu_buffer, head))
|
return -1;
|
|
list_for_each_entry_safe(bpage, tmp, head, list) {
|
if (RB_WARN_ON(cpu_buffer,
|
bpage->list.next->prev != &bpage->list))
|
return -1;
|
if (RB_WARN_ON(cpu_buffer,
|
bpage->list.prev->next != &bpage->list))
|
return -1;
|
if (rb_check_list(cpu_buffer, &bpage->list))
|
return -1;
|
}
|
|
rb_head_page_activate(cpu_buffer);
|
|
return 0;
|
}
|
|
static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
|
{
|
struct buffer_page *bpage, *tmp;
|
bool user_thread = current->mm != NULL;
|
gfp_t mflags;
|
long i;
|
|
/*
|
* Check if the available memory is there first.
|
* Note, si_mem_available() only gives us a rough estimate of available
|
* memory. It may not be accurate. But we don't care, we just want
|
* to prevent doing any allocation when it is obvious that it is
|
* not going to succeed.
|
*/
|
i = si_mem_available();
|
if (i < nr_pages)
|
return -ENOMEM;
|
|
/*
|
* __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
|
* gracefully without invoking oom-killer and the system is not
|
* destabilized.
|
*/
|
mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
|
|
/*
|
* If a user thread allocates too much, and si_mem_available()
|
* reports there's enough memory, even though there is not.
|
* Make sure the OOM killer kills this thread. This can happen
|
* even with RETRY_MAYFAIL because another task may be doing
|
* an allocation after this task has taken all memory.
|
* This is the task the OOM killer needs to take out during this
|
* loop, even if it was triggered by an allocation somewhere else.
|
*/
|
if (user_thread)
|
set_current_oom_origin();
|
for (i = 0; i < nr_pages; i++) {
|
struct page *page;
|
|
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
|
mflags, cpu_to_node(cpu));
|
if (!bpage)
|
goto free_pages;
|
|
list_add(&bpage->list, pages);
|
|
page = alloc_pages_node(cpu_to_node(cpu), mflags, 0);
|
if (!page)
|
goto free_pages;
|
bpage->page = page_address(page);
|
rb_init_page(bpage->page);
|
|
if (user_thread && fatal_signal_pending(current))
|
goto free_pages;
|
}
|
if (user_thread)
|
clear_current_oom_origin();
|
|
return 0;
|
|
free_pages:
|
list_for_each_entry_safe(bpage, tmp, pages, list) {
|
list_del_init(&bpage->list);
|
free_buffer_page(bpage);
|
}
|
if (user_thread)
|
clear_current_oom_origin();
|
|
return -ENOMEM;
|
}
|
|
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
|
unsigned long nr_pages)
|
{
|
LIST_HEAD(pages);
|
|
WARN_ON(!nr_pages);
|
|
if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
|
return -ENOMEM;
|
|
/*
|
* The ring buffer page list is a circular list that does not
|
* start and end with a list head. All page list items point to
|
* other pages.
|
*/
|
cpu_buffer->pages = pages.next;
|
list_del(&pages);
|
|
cpu_buffer->nr_pages = nr_pages;
|
|
rb_check_pages(cpu_buffer);
|
|
return 0;
|
}
|
|
static struct ring_buffer_per_cpu *
|
rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
struct buffer_page *bpage;
|
struct page *page;
|
int ret;
|
|
cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
|
GFP_KERNEL, cpu_to_node(cpu));
|
if (!cpu_buffer)
|
return NULL;
|
|
cpu_buffer->cpu = cpu;
|
cpu_buffer->buffer = buffer;
|
raw_spin_lock_init(&cpu_buffer->reader_lock);
|
lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
|
cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
|
INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
|
init_completion(&cpu_buffer->update_done);
|
init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
|
init_waitqueue_head(&cpu_buffer->irq_work.waiters);
|
init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
|
|
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
|
GFP_KERNEL, cpu_to_node(cpu));
|
if (!bpage)
|
goto fail_free_buffer;
|
|
rb_check_bpage(cpu_buffer, bpage);
|
|
cpu_buffer->reader_page = bpage;
|
page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
|
if (!page)
|
goto fail_free_reader;
|
bpage->page = page_address(page);
|
rb_init_page(bpage->page);
|
|
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
|
ret = rb_allocate_pages(cpu_buffer, nr_pages);
|
if (ret < 0)
|
goto fail_free_reader;
|
|
cpu_buffer->head_page
|
= list_entry(cpu_buffer->pages, struct buffer_page, list);
|
cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
|
|
rb_head_page_activate(cpu_buffer);
|
|
return cpu_buffer;
|
|
fail_free_reader:
|
free_buffer_page(cpu_buffer->reader_page);
|
|
fail_free_buffer:
|
kfree(cpu_buffer);
|
return NULL;
|
}
|
|
static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
struct list_head *head = cpu_buffer->pages;
|
struct buffer_page *bpage, *tmp;
|
|
free_buffer_page(cpu_buffer->reader_page);
|
|
if (head) {
|
rb_head_page_deactivate(cpu_buffer);
|
|
list_for_each_entry_safe(bpage, tmp, head, list) {
|
list_del_init(&bpage->list);
|
free_buffer_page(bpage);
|
}
|
bpage = list_entry(head, struct buffer_page, list);
|
free_buffer_page(bpage);
|
}
|
|
kfree(cpu_buffer);
|
}
|
|
/**
|
* __ring_buffer_alloc - allocate a new ring_buffer
|
* @size: the size in bytes per cpu that is needed.
|
* @flags: attributes to set for the ring buffer.
|
* @key: ring buffer reader_lock_key.
|
*
|
* Currently the only flag that is available is the RB_FL_OVERWRITE
|
* flag. This flag means that the buffer will overwrite old data
|
* when the buffer wraps. If this flag is not set, the buffer will
|
* drop data when the tail hits the head.
|
*/
|
struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
|
struct lock_class_key *key)
|
{
|
struct trace_buffer *buffer;
|
long nr_pages;
|
int bsize;
|
int cpu;
|
int ret;
|
|
/* keep it in its own cache line */
|
buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
|
GFP_KERNEL);
|
if (!buffer)
|
return NULL;
|
|
if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
|
goto fail_free_buffer;
|
|
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
|
buffer->flags = flags;
|
buffer->clock = trace_clock_local;
|
buffer->reader_lock_key = key;
|
|
init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
|
init_waitqueue_head(&buffer->irq_work.waiters);
|
|
/* need at least two pages */
|
if (nr_pages < 2)
|
nr_pages = 2;
|
|
buffer->cpus = nr_cpu_ids;
|
|
bsize = sizeof(void *) * nr_cpu_ids;
|
buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
|
GFP_KERNEL);
|
if (!buffer->buffers)
|
goto fail_free_cpumask;
|
|
cpu = raw_smp_processor_id();
|
cpumask_set_cpu(cpu, buffer->cpumask);
|
buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
|
if (!buffer->buffers[cpu])
|
goto fail_free_buffers;
|
|
ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
|
if (ret < 0)
|
goto fail_free_buffers;
|
|
mutex_init(&buffer->mutex);
|
|
return buffer;
|
|
fail_free_buffers:
|
for_each_buffer_cpu(buffer, cpu) {
|
if (buffer->buffers[cpu])
|
rb_free_cpu_buffer(buffer->buffers[cpu]);
|
}
|
kfree(buffer->buffers);
|
|
fail_free_cpumask:
|
free_cpumask_var(buffer->cpumask);
|
|
fail_free_buffer:
|
kfree(buffer);
|
return NULL;
|
}
|
EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
|
|
/**
|
* ring_buffer_free - free a ring buffer.
|
* @buffer: the buffer to free.
|
*/
|
void
|
ring_buffer_free(struct trace_buffer *buffer)
|
{
|
int cpu;
|
|
cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
|
|
for_each_buffer_cpu(buffer, cpu)
|
rb_free_cpu_buffer(buffer->buffers[cpu]);
|
|
kfree(buffer->buffers);
|
free_cpumask_var(buffer->cpumask);
|
|
kfree(buffer);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_free);
|
|
void ring_buffer_set_clock(struct trace_buffer *buffer,
|
u64 (*clock)(void))
|
{
|
buffer->clock = clock;
|
}
|
|
void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
|
{
|
buffer->time_stamp_abs = abs;
|
}
|
|
bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
|
{
|
return buffer->time_stamp_abs;
|
}
|
|
static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
|
|
static inline unsigned long rb_page_entries(struct buffer_page *bpage)
|
{
|
return local_read(&bpage->entries) & RB_WRITE_MASK;
|
}
|
|
static inline unsigned long rb_page_write(struct buffer_page *bpage)
|
{
|
return local_read(&bpage->write) & RB_WRITE_MASK;
|
}
|
|
static int
|
rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
|
{
|
struct list_head *tail_page, *to_remove, *next_page;
|
struct buffer_page *to_remove_page, *tmp_iter_page;
|
struct buffer_page *last_page, *first_page;
|
unsigned long nr_removed;
|
unsigned long head_bit;
|
int page_entries;
|
|
head_bit = 0;
|
|
raw_spin_lock_irq(&cpu_buffer->reader_lock);
|
atomic_inc(&cpu_buffer->record_disabled);
|
/*
|
* We don't race with the readers since we have acquired the reader
|
* lock. We also don't race with writers after disabling recording.
|
* This makes it easy to figure out the first and the last page to be
|
* removed from the list. We unlink all the pages in between including
|
* the first and last pages. This is done in a busy loop so that we
|
* lose the least number of traces.
|
* The pages are freed after we restart recording and unlock readers.
|
*/
|
tail_page = &cpu_buffer->tail_page->list;
|
|
/*
|
* tail page might be on reader page, we remove the next page
|
* from the ring buffer
|
*/
|
if (cpu_buffer->tail_page == cpu_buffer->reader_page)
|
tail_page = rb_list_head(tail_page->next);
|
to_remove = tail_page;
|
|
/* start of pages to remove */
|
first_page = list_entry(rb_list_head(to_remove->next),
|
struct buffer_page, list);
|
|
for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
|
to_remove = rb_list_head(to_remove)->next;
|
head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
|
}
|
|
next_page = rb_list_head(to_remove)->next;
|
|
/*
|
* Now we remove all pages between tail_page and next_page.
|
* Make sure that we have head_bit value preserved for the
|
* next page
|
*/
|
tail_page->next = (struct list_head *)((unsigned long)next_page |
|
head_bit);
|
next_page = rb_list_head(next_page);
|
next_page->prev = tail_page;
|
|
/* make sure pages points to a valid page in the ring buffer */
|
cpu_buffer->pages = next_page;
|
|
/* update head page */
|
if (head_bit)
|
cpu_buffer->head_page = list_entry(next_page,
|
struct buffer_page, list);
|
|
/*
|
* change read pointer to make sure any read iterators reset
|
* themselves
|
*/
|
cpu_buffer->read = 0;
|
|
/* pages are removed, resume tracing and then free the pages */
|
atomic_dec(&cpu_buffer->record_disabled);
|
raw_spin_unlock_irq(&cpu_buffer->reader_lock);
|
|
RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
|
|
/* last buffer page to remove */
|
last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
|
list);
|
tmp_iter_page = first_page;
|
|
do {
|
cond_resched();
|
|
to_remove_page = tmp_iter_page;
|
rb_inc_page(cpu_buffer, &tmp_iter_page);
|
|
/* update the counters */
|
page_entries = rb_page_entries(to_remove_page);
|
if (page_entries) {
|
/*
|
* If something was added to this page, it was full
|
* since it is not the tail page. So we deduct the
|
* bytes consumed in ring buffer from here.
|
* Increment overrun to account for the lost events.
|
*/
|
local_add(page_entries, &cpu_buffer->overrun);
|
local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
|
local_inc(&cpu_buffer->pages_lost);
|
}
|
|
/*
|
* We have already removed references to this list item, just
|
* free up the buffer_page and its page
|
*/
|
free_buffer_page(to_remove_page);
|
nr_removed--;
|
|
} while (to_remove_page != last_page);
|
|
RB_WARN_ON(cpu_buffer, nr_removed);
|
|
return nr_removed == 0;
|
}
|
|
static int
|
rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
struct list_head *pages = &cpu_buffer->new_pages;
|
int retries, success;
|
|
raw_spin_lock_irq(&cpu_buffer->reader_lock);
|
/*
|
* We are holding the reader lock, so the reader page won't be swapped
|
* in the ring buffer. Now we are racing with the writer trying to
|
* move head page and the tail page.
|
* We are going to adapt the reader page update process where:
|
* 1. We first splice the start and end of list of new pages between
|
* the head page and its previous page.
|
* 2. We cmpxchg the prev_page->next to point from head page to the
|
* start of new pages list.
|
* 3. Finally, we update the head->prev to the end of new list.
|
*
|
* We will try this process 10 times, to make sure that we don't keep
|
* spinning.
|
*/
|
retries = 10;
|
success = 0;
|
while (retries--) {
|
struct list_head *head_page, *prev_page, *r;
|
struct list_head *last_page, *first_page;
|
struct list_head *head_page_with_bit;
|
|
head_page = &rb_set_head_page(cpu_buffer)->list;
|
if (!head_page)
|
break;
|
prev_page = head_page->prev;
|
|
first_page = pages->next;
|
last_page = pages->prev;
|
|
head_page_with_bit = (struct list_head *)
|
((unsigned long)head_page | RB_PAGE_HEAD);
|
|
last_page->next = head_page_with_bit;
|
first_page->prev = prev_page;
|
|
r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
|
|
if (r == head_page_with_bit) {
|
/*
|
* yay, we replaced the page pointer to our new list,
|
* now, we just have to update to head page's prev
|
* pointer to point to end of list
|
*/
|
head_page->prev = last_page;
|
success = 1;
|
break;
|
}
|
}
|
|
if (success)
|
INIT_LIST_HEAD(pages);
|
/*
|
* If we weren't successful in adding in new pages, warn and stop
|
* tracing
|
*/
|
RB_WARN_ON(cpu_buffer, !success);
|
raw_spin_unlock_irq(&cpu_buffer->reader_lock);
|
|
/* free pages if they weren't inserted */
|
if (!success) {
|
struct buffer_page *bpage, *tmp;
|
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
|
list) {
|
list_del_init(&bpage->list);
|
free_buffer_page(bpage);
|
}
|
}
|
return success;
|
}
|
|
static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
int success;
|
|
if (cpu_buffer->nr_pages_to_update > 0)
|
success = rb_insert_pages(cpu_buffer);
|
else
|
success = rb_remove_pages(cpu_buffer,
|
-cpu_buffer->nr_pages_to_update);
|
|
if (success)
|
cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
|
}
|
|
static void update_pages_handler(struct work_struct *work)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
|
struct ring_buffer_per_cpu, update_pages_work);
|
rb_update_pages(cpu_buffer);
|
complete(&cpu_buffer->update_done);
|
}
|
|
/**
|
* ring_buffer_resize - resize the ring buffer
|
* @buffer: the buffer to resize.
|
* @size: the new size.
|
* @cpu_id: the cpu buffer to resize
|
*
|
* Minimum size is 2 * BUF_PAGE_SIZE.
|
*
|
* Returns 0 on success and < 0 on failure.
|
*/
|
int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
|
int cpu_id)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
unsigned long nr_pages;
|
int cpu, err;
|
|
/*
|
* Always succeed at resizing a non-existent buffer:
|
*/
|
if (!buffer)
|
return 0;
|
|
/* Make sure the requested buffer exists */
|
if (cpu_id != RING_BUFFER_ALL_CPUS &&
|
!cpumask_test_cpu(cpu_id, buffer->cpumask))
|
return 0;
|
|
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
|
|
/* we need a minimum of two pages */
|
if (nr_pages < 2)
|
nr_pages = 2;
|
|
size = nr_pages * BUF_PAGE_SIZE;
|
|
/* prevent another thread from changing buffer sizes */
|
mutex_lock(&buffer->mutex);
|
|
|
if (cpu_id == RING_BUFFER_ALL_CPUS) {
|
/*
|
* Don't succeed if resizing is disabled, as a reader might be
|
* manipulating the ring buffer and is expecting a sane state while
|
* this is true.
|
*/
|
for_each_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
if (atomic_read(&cpu_buffer->resize_disabled)) {
|
err = -EBUSY;
|
goto out_err_unlock;
|
}
|
}
|
|
/* calculate the pages to update */
|
for_each_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
|
cpu_buffer->nr_pages_to_update = nr_pages -
|
cpu_buffer->nr_pages;
|
/*
|
* nothing more to do for removing pages or no update
|
*/
|
if (cpu_buffer->nr_pages_to_update <= 0)
|
continue;
|
/*
|
* to add pages, make sure all new pages can be
|
* allocated without receiving ENOMEM
|
*/
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
|
&cpu_buffer->new_pages, cpu)) {
|
/* not enough memory for new pages */
|
err = -ENOMEM;
|
goto out_err;
|
}
|
}
|
|
get_online_cpus();
|
/*
|
* Fire off all the required work handlers
|
* We can't schedule on offline CPUs, but it's not necessary
|
* since we can change their buffer sizes without any race.
|
*/
|
for_each_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
if (!cpu_buffer->nr_pages_to_update)
|
continue;
|
|
/* Can't run something on an offline CPU. */
|
if (!cpu_online(cpu)) {
|
rb_update_pages(cpu_buffer);
|
cpu_buffer->nr_pages_to_update = 0;
|
} else {
|
schedule_work_on(cpu,
|
&cpu_buffer->update_pages_work);
|
}
|
}
|
|
/* wait for all the updates to complete */
|
for_each_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
if (!cpu_buffer->nr_pages_to_update)
|
continue;
|
|
if (cpu_online(cpu))
|
wait_for_completion(&cpu_buffer->update_done);
|
cpu_buffer->nr_pages_to_update = 0;
|
}
|
|
put_online_cpus();
|
} else {
|
/* Make sure this CPU has been initialized */
|
if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
|
goto out;
|
|
cpu_buffer = buffer->buffers[cpu_id];
|
|
if (nr_pages == cpu_buffer->nr_pages)
|
goto out;
|
|
/*
|
* Don't succeed if resizing is disabled, as a reader might be
|
* manipulating the ring buffer and is expecting a sane state while
|
* this is true.
|
*/
|
if (atomic_read(&cpu_buffer->resize_disabled)) {
|
err = -EBUSY;
|
goto out_err_unlock;
|
}
|
|
cpu_buffer->nr_pages_to_update = nr_pages -
|
cpu_buffer->nr_pages;
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
if (cpu_buffer->nr_pages_to_update > 0 &&
|
__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
|
&cpu_buffer->new_pages, cpu_id)) {
|
err = -ENOMEM;
|
goto out_err;
|
}
|
|
get_online_cpus();
|
|
/* Can't run something on an offline CPU. */
|
if (!cpu_online(cpu_id))
|
rb_update_pages(cpu_buffer);
|
else {
|
schedule_work_on(cpu_id,
|
&cpu_buffer->update_pages_work);
|
wait_for_completion(&cpu_buffer->update_done);
|
}
|
|
cpu_buffer->nr_pages_to_update = 0;
|
put_online_cpus();
|
}
|
|
out:
|
/*
|
* The ring buffer resize can happen with the ring buffer
|
* enabled, so that the update disturbs the tracing as little
|
* as possible. But if the buffer is disabled, we do not need
|
* to worry about that, and we can take the time to verify
|
* that the buffer is not corrupt.
|
*/
|
if (atomic_read(&buffer->record_disabled)) {
|
atomic_inc(&buffer->record_disabled);
|
/*
|
* Even though the buffer was disabled, we must make sure
|
* that it is truly disabled before calling rb_check_pages.
|
* There could have been a race between checking
|
* record_disable and incrementing it.
|
*/
|
synchronize_rcu();
|
for_each_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
rb_check_pages(cpu_buffer);
|
}
|
atomic_dec(&buffer->record_disabled);
|
}
|
|
mutex_unlock(&buffer->mutex);
|
return 0;
|
|
out_err:
|
for_each_buffer_cpu(buffer, cpu) {
|
struct buffer_page *bpage, *tmp;
|
|
cpu_buffer = buffer->buffers[cpu];
|
cpu_buffer->nr_pages_to_update = 0;
|
|
if (list_empty(&cpu_buffer->new_pages))
|
continue;
|
|
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
|
list) {
|
list_del_init(&bpage->list);
|
free_buffer_page(bpage);
|
}
|
}
|
out_err_unlock:
|
mutex_unlock(&buffer->mutex);
|
return err;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_resize);
|
|
void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
|
{
|
mutex_lock(&buffer->mutex);
|
if (val)
|
buffer->flags |= RB_FL_OVERWRITE;
|
else
|
buffer->flags &= ~RB_FL_OVERWRITE;
|
mutex_unlock(&buffer->mutex);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
|
|
static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
|
{
|
return bpage->page->data + index;
|
}
|
|
static __always_inline struct ring_buffer_event *
|
rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
return __rb_page_index(cpu_buffer->reader_page,
|
cpu_buffer->reader_page->read);
|
}
|
|
static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
|
{
|
return local_read(&bpage->page->commit);
|
}
|
|
static struct ring_buffer_event *
|
rb_iter_head_event(struct ring_buffer_iter *iter)
|
{
|
struct ring_buffer_event *event;
|
struct buffer_page *iter_head_page = iter->head_page;
|
unsigned long commit;
|
unsigned length;
|
|
if (iter->head != iter->next_event)
|
return iter->event;
|
|
/*
|
* When the writer goes across pages, it issues a cmpxchg which
|
* is a mb(), which will synchronize with the rmb here.
|
* (see rb_tail_page_update() and __rb_reserve_next())
|
*/
|
commit = rb_page_commit(iter_head_page);
|
smp_rmb();
|
event = __rb_page_index(iter_head_page, iter->head);
|
length = rb_event_length(event);
|
|
/*
|
* READ_ONCE() doesn't work on functions and we don't want the
|
* compiler doing any crazy optimizations with length.
|
*/
|
barrier();
|
|
if ((iter->head + length) > commit || length > BUF_MAX_DATA_SIZE)
|
/* Writer corrupted the read? */
|
goto reset;
|
|
memcpy(iter->event, event, length);
|
/*
|
* If the page stamp is still the same after this rmb() then the
|
* event was safely copied without the writer entering the page.
|
*/
|
smp_rmb();
|
|
/* Make sure the page didn't change since we read this */
|
if (iter->page_stamp != iter_head_page->page->time_stamp ||
|
commit > rb_page_commit(iter_head_page))
|
goto reset;
|
|
iter->next_event = iter->head + length;
|
return iter->event;
|
reset:
|
/* Reset to the beginning */
|
iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
|
iter->head = 0;
|
iter->next_event = 0;
|
iter->missed_events = 1;
|
return NULL;
|
}
|
|
/* Size is determined by what has been committed */
|
static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
|
{
|
return rb_page_commit(bpage);
|
}
|
|
static __always_inline unsigned
|
rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
return rb_page_commit(cpu_buffer->commit_page);
|
}
|
|
static __always_inline unsigned
|
rb_event_index(struct ring_buffer_event *event)
|
{
|
unsigned long addr = (unsigned long)event;
|
|
return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
|
}
|
|
static void rb_inc_iter(struct ring_buffer_iter *iter)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
/*
|
* The iterator could be on the reader page (it starts there).
|
* But the head could have moved, since the reader was
|
* found. Check for this case and assign the iterator
|
* to the head page instead of next.
|
*/
|
if (iter->head_page == cpu_buffer->reader_page)
|
iter->head_page = rb_set_head_page(cpu_buffer);
|
else
|
rb_inc_page(cpu_buffer, &iter->head_page);
|
|
iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
|
iter->head = 0;
|
iter->next_event = 0;
|
}
|
|
/*
|
* rb_handle_head_page - writer hit the head page
|
*
|
* Returns: +1 to retry page
|
* 0 to continue
|
* -1 on error
|
*/
|
static int
|
rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
|
struct buffer_page *tail_page,
|
struct buffer_page *next_page)
|
{
|
struct buffer_page *new_head;
|
int entries;
|
int type;
|
int ret;
|
|
entries = rb_page_entries(next_page);
|
|
/*
|
* The hard part is here. We need to move the head
|
* forward, and protect against both readers on
|
* other CPUs and writers coming in via interrupts.
|
*/
|
type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
|
RB_PAGE_HEAD);
|
|
/*
|
* type can be one of four:
|
* NORMAL - an interrupt already moved it for us
|
* HEAD - we are the first to get here.
|
* UPDATE - we are the interrupt interrupting
|
* a current move.
|
* MOVED - a reader on another CPU moved the next
|
* pointer to its reader page. Give up
|
* and try again.
|
*/
|
|
switch (type) {
|
case RB_PAGE_HEAD:
|
/*
|
* We changed the head to UPDATE, thus
|
* it is our responsibility to update
|
* the counters.
|
*/
|
local_add(entries, &cpu_buffer->overrun);
|
local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
|
local_inc(&cpu_buffer->pages_lost);
|
|
/*
|
* The entries will be zeroed out when we move the
|
* tail page.
|
*/
|
|
/* still more to do */
|
break;
|
|
case RB_PAGE_UPDATE:
|
/*
|
* This is an interrupt that interrupt the
|
* previous update. Still more to do.
|
*/
|
break;
|
case RB_PAGE_NORMAL:
|
/*
|
* An interrupt came in before the update
|
* and processed this for us.
|
* Nothing left to do.
|
*/
|
return 1;
|
case RB_PAGE_MOVED:
|
/*
|
* The reader is on another CPU and just did
|
* a swap with our next_page.
|
* Try again.
|
*/
|
return 1;
|
default:
|
RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
|
return -1;
|
}
|
|
/*
|
* Now that we are here, the old head pointer is
|
* set to UPDATE. This will keep the reader from
|
* swapping the head page with the reader page.
|
* The reader (on another CPU) will spin till
|
* we are finished.
|
*
|
* We just need to protect against interrupts
|
* doing the job. We will set the next pointer
|
* to HEAD. After that, we set the old pointer
|
* to NORMAL, but only if it was HEAD before.
|
* otherwise we are an interrupt, and only
|
* want the outer most commit to reset it.
|
*/
|
new_head = next_page;
|
rb_inc_page(cpu_buffer, &new_head);
|
|
ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
|
RB_PAGE_NORMAL);
|
|
/*
|
* Valid returns are:
|
* HEAD - an interrupt came in and already set it.
|
* NORMAL - One of two things:
|
* 1) We really set it.
|
* 2) A bunch of interrupts came in and moved
|
* the page forward again.
|
*/
|
switch (ret) {
|
case RB_PAGE_HEAD:
|
case RB_PAGE_NORMAL:
|
/* OK */
|
break;
|
default:
|
RB_WARN_ON(cpu_buffer, 1);
|
return -1;
|
}
|
|
/*
|
* It is possible that an interrupt came in,
|
* set the head up, then more interrupts came in
|
* and moved it again. When we get back here,
|
* the page would have been set to NORMAL but we
|
* just set it back to HEAD.
|
*
|
* How do you detect this? Well, if that happened
|
* the tail page would have moved.
|
*/
|
if (ret == RB_PAGE_NORMAL) {
|
struct buffer_page *buffer_tail_page;
|
|
buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
|
/*
|
* If the tail had moved passed next, then we need
|
* to reset the pointer.
|
*/
|
if (buffer_tail_page != tail_page &&
|
buffer_tail_page != next_page)
|
rb_head_page_set_normal(cpu_buffer, new_head,
|
next_page,
|
RB_PAGE_HEAD);
|
}
|
|
/*
|
* If this was the outer most commit (the one that
|
* changed the original pointer from HEAD to UPDATE),
|
* then it is up to us to reset it to NORMAL.
|
*/
|
if (type == RB_PAGE_HEAD) {
|
ret = rb_head_page_set_normal(cpu_buffer, next_page,
|
tail_page,
|
RB_PAGE_UPDATE);
|
if (RB_WARN_ON(cpu_buffer,
|
ret != RB_PAGE_UPDATE))
|
return -1;
|
}
|
|
return 0;
|
}
|
|
static inline void
|
rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
|
unsigned long tail, struct rb_event_info *info)
|
{
|
struct buffer_page *tail_page = info->tail_page;
|
struct ring_buffer_event *event;
|
unsigned long length = info->length;
|
|
/*
|
* Only the event that crossed the page boundary
|
* must fill the old tail_page with padding.
|
*/
|
if (tail >= BUF_PAGE_SIZE) {
|
/*
|
* If the page was filled, then we still need
|
* to update the real_end. Reset it to zero
|
* and the reader will ignore it.
|
*/
|
if (tail == BUF_PAGE_SIZE)
|
tail_page->real_end = 0;
|
|
local_sub(length, &tail_page->write);
|
return;
|
}
|
|
event = __rb_page_index(tail_page, tail);
|
|
/* account for padding bytes */
|
local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
|
|
/*
|
* Save the original length to the meta data.
|
* This will be used by the reader to add lost event
|
* counter.
|
*/
|
tail_page->real_end = tail;
|
|
/*
|
* If this event is bigger than the minimum size, then
|
* we need to be careful that we don't subtract the
|
* write counter enough to allow another writer to slip
|
* in on this page.
|
* We put in a discarded commit instead, to make sure
|
* that this space is not used again.
|
*
|
* If we are less than the minimum size, we don't need to
|
* worry about it.
|
*/
|
if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
|
/* No room for any events */
|
|
/* Mark the rest of the page with padding */
|
rb_event_set_padding(event);
|
|
/* Make sure the padding is visible before the write update */
|
smp_wmb();
|
|
/* Set the write back to the previous setting */
|
local_sub(length, &tail_page->write);
|
return;
|
}
|
|
/* Put in a discarded event */
|
event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
|
event->type_len = RINGBUF_TYPE_PADDING;
|
/* time delta must be non zero */
|
event->time_delta = 1;
|
|
/* Make sure the padding is visible before the tail_page->write update */
|
smp_wmb();
|
|
/* Set write to end of buffer */
|
length = (tail + length) - BUF_PAGE_SIZE;
|
local_sub(length, &tail_page->write);
|
}
|
|
static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
|
|
/*
|
* This is the slow path, force gcc not to inline it.
|
*/
|
static noinline struct ring_buffer_event *
|
rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
|
unsigned long tail, struct rb_event_info *info)
|
{
|
struct buffer_page *tail_page = info->tail_page;
|
struct buffer_page *commit_page = cpu_buffer->commit_page;
|
struct trace_buffer *buffer = cpu_buffer->buffer;
|
struct buffer_page *next_page;
|
int ret;
|
|
next_page = tail_page;
|
|
rb_inc_page(cpu_buffer, &next_page);
|
|
/*
|
* If for some reason, we had an interrupt storm that made
|
* it all the way around the buffer, bail, and warn
|
* about it.
|
*/
|
if (unlikely(next_page == commit_page)) {
|
local_inc(&cpu_buffer->commit_overrun);
|
goto out_reset;
|
}
|
|
/*
|
* This is where the fun begins!
|
*
|
* We are fighting against races between a reader that
|
* could be on another CPU trying to swap its reader
|
* page with the buffer head.
|
*
|
* We are also fighting against interrupts coming in and
|
* moving the head or tail on us as well.
|
*
|
* If the next page is the head page then we have filled
|
* the buffer, unless the commit page is still on the
|
* reader page.
|
*/
|
if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
|
|
/*
|
* If the commit is not on the reader page, then
|
* move the header page.
|
*/
|
if (!rb_is_reader_page(cpu_buffer->commit_page)) {
|
/*
|
* If we are not in overwrite mode,
|
* this is easy, just stop here.
|
*/
|
if (!(buffer->flags & RB_FL_OVERWRITE)) {
|
local_inc(&cpu_buffer->dropped_events);
|
goto out_reset;
|
}
|
|
ret = rb_handle_head_page(cpu_buffer,
|
tail_page,
|
next_page);
|
if (ret < 0)
|
goto out_reset;
|
if (ret)
|
goto out_again;
|
} else {
|
/*
|
* We need to be careful here too. The
|
* commit page could still be on the reader
|
* page. We could have a small buffer, and
|
* have filled up the buffer with events
|
* from interrupts and such, and wrapped.
|
*
|
* Note, if the tail page is also the on the
|
* reader_page, we let it move out.
|
*/
|
if (unlikely((cpu_buffer->commit_page !=
|
cpu_buffer->tail_page) &&
|
(cpu_buffer->commit_page ==
|
cpu_buffer->reader_page))) {
|
local_inc(&cpu_buffer->commit_overrun);
|
goto out_reset;
|
}
|
}
|
}
|
|
rb_tail_page_update(cpu_buffer, tail_page, next_page);
|
|
out_again:
|
|
rb_reset_tail(cpu_buffer, tail, info);
|
|
/* Commit what we have for now. */
|
rb_end_commit(cpu_buffer);
|
/* rb_end_commit() decs committing */
|
local_inc(&cpu_buffer->committing);
|
|
/* fail and let the caller try again */
|
return ERR_PTR(-EAGAIN);
|
|
out_reset:
|
/* reset write */
|
rb_reset_tail(cpu_buffer, tail, info);
|
|
return NULL;
|
}
|
|
/* Slow path */
|
static struct ring_buffer_event *
|
rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
|
{
|
if (abs)
|
event->type_len = RINGBUF_TYPE_TIME_STAMP;
|
else
|
event->type_len = RINGBUF_TYPE_TIME_EXTEND;
|
|
/* Not the first event on the page, or not delta? */
|
if (abs || rb_event_index(event)) {
|
event->time_delta = delta & TS_MASK;
|
event->array[0] = delta >> TS_SHIFT;
|
} else {
|
/* nope, just zero it */
|
event->time_delta = 0;
|
event->array[0] = 0;
|
}
|
|
return skip_time_extend(event);
|
}
|
|
static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
|
struct ring_buffer_event *event);
|
|
#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
|
static inline bool sched_clock_stable(void)
|
{
|
return true;
|
}
|
#endif
|
|
static void
|
rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
|
struct rb_event_info *info)
|
{
|
u64 write_stamp;
|
|
WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
|
(unsigned long long)info->delta,
|
(unsigned long long)info->ts,
|
(unsigned long long)info->before,
|
(unsigned long long)info->after,
|
(unsigned long long)(rb_time_read(&cpu_buffer->write_stamp, &write_stamp) ? write_stamp : 0),
|
sched_clock_stable() ? "" :
|
"If you just came from a suspend/resume,\n"
|
"please switch to the trace global clock:\n"
|
" echo global > /sys/kernel/debug/tracing/trace_clock\n"
|
"or add trace_clock=global to the kernel command line\n");
|
}
|
|
static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
|
struct ring_buffer_event **event,
|
struct rb_event_info *info,
|
u64 *delta,
|
unsigned int *length)
|
{
|
bool abs = info->add_timestamp &
|
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
|
|
if (unlikely(info->delta > (1ULL << 59))) {
|
/* did the clock go backwards */
|
if (info->before == info->after && info->before > info->ts) {
|
/* not interrupted */
|
static int once;
|
|
/*
|
* This is possible with a recalibrating of the TSC.
|
* Do not produce a call stack, but just report it.
|
*/
|
if (!once) {
|
once++;
|
pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
|
info->before, info->ts);
|
}
|
} else
|
rb_check_timestamp(cpu_buffer, info);
|
if (!abs)
|
info->delta = 0;
|
}
|
*event = rb_add_time_stamp(*event, info->delta, abs);
|
*length -= RB_LEN_TIME_EXTEND;
|
*delta = 0;
|
}
|
|
/**
|
* rb_update_event - update event type and data
|
* @cpu_buffer: The per cpu buffer of the @event
|
* @event: the event to update
|
* @info: The info to update the @event with (contains length and delta)
|
*
|
* Update the type and data fields of the @event. The length
|
* is the actual size that is written to the ring buffer,
|
* and with this, we can determine what to place into the
|
* data field.
|
*/
|
static void
|
rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
|
struct ring_buffer_event *event,
|
struct rb_event_info *info)
|
{
|
unsigned length = info->length;
|
u64 delta = info->delta;
|
|
/*
|
* If we need to add a timestamp, then we
|
* add it to the start of the reserved space.
|
*/
|
if (unlikely(info->add_timestamp))
|
rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
|
|
event->time_delta = delta;
|
length -= RB_EVNT_HDR_SIZE;
|
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
|
event->type_len = 0;
|
event->array[0] = length;
|
} else
|
event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
|
}
|
|
static unsigned rb_calculate_event_length(unsigned length)
|
{
|
struct ring_buffer_event event; /* Used only for sizeof array */
|
|
/* zero length can cause confusions */
|
if (!length)
|
length++;
|
|
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
|
length += sizeof(event.array[0]);
|
|
length += RB_EVNT_HDR_SIZE;
|
length = ALIGN(length, RB_ARCH_ALIGNMENT);
|
|
/*
|
* In case the time delta is larger than the 27 bits for it
|
* in the header, we need to add a timestamp. If another
|
* event comes in when trying to discard this one to increase
|
* the length, then the timestamp will be added in the allocated
|
* space of this event. If length is bigger than the size needed
|
* for the TIME_EXTEND, then padding has to be used. The events
|
* length must be either RB_LEN_TIME_EXTEND, or greater than or equal
|
* to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
|
* As length is a multiple of 4, we only need to worry if it
|
* is 12 (RB_LEN_TIME_EXTEND + 4).
|
*/
|
if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
|
length += RB_ALIGNMENT;
|
|
return length;
|
}
|
|
static __always_inline bool
|
rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
|
struct ring_buffer_event *event)
|
{
|
unsigned long addr = (unsigned long)event;
|
unsigned long index;
|
|
index = rb_event_index(event);
|
addr &= PAGE_MASK;
|
|
return cpu_buffer->commit_page->page == (void *)addr &&
|
rb_commit_index(cpu_buffer) == index;
|
}
|
|
static u64 rb_time_delta(struct ring_buffer_event *event)
|
{
|
switch (event->type_len) {
|
case RINGBUF_TYPE_PADDING:
|
return 0;
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
return ring_buffer_event_time_stamp(event);
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
return 0;
|
|
case RINGBUF_TYPE_DATA:
|
return event->time_delta;
|
default:
|
return 0;
|
}
|
}
|
|
static inline int
|
rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
|
struct ring_buffer_event *event)
|
{
|
unsigned long new_index, old_index;
|
struct buffer_page *bpage;
|
unsigned long index;
|
unsigned long addr;
|
u64 write_stamp;
|
u64 delta;
|
|
new_index = rb_event_index(event);
|
old_index = new_index + rb_event_ts_length(event);
|
addr = (unsigned long)event;
|
addr &= PAGE_MASK;
|
|
bpage = READ_ONCE(cpu_buffer->tail_page);
|
|
delta = rb_time_delta(event);
|
|
if (!rb_time_read(&cpu_buffer->write_stamp, &write_stamp))
|
return 0;
|
|
/* Make sure the write stamp is read before testing the location */
|
barrier();
|
|
if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
|
unsigned long write_mask =
|
local_read(&bpage->write) & ~RB_WRITE_MASK;
|
unsigned long event_length = rb_event_length(event);
|
|
/* Something came in, can't discard */
|
if (!rb_time_cmpxchg(&cpu_buffer->write_stamp,
|
write_stamp, write_stamp - delta))
|
return 0;
|
|
/*
|
* It's possible that the event time delta is zero
|
* (has the same time stamp as the previous event)
|
* in which case write_stamp and before_stamp could
|
* be the same. In such a case, force before_stamp
|
* to be different than write_stamp. It doesn't
|
* matter what it is, as long as its different.
|
*/
|
if (!delta)
|
rb_time_set(&cpu_buffer->before_stamp, 0);
|
|
/*
|
* If an event were to come in now, it would see that the
|
* write_stamp and the before_stamp are different, and assume
|
* that this event just added itself before updating
|
* the write stamp. The interrupting event will fix the
|
* write stamp for us, and use the before stamp as its delta.
|
*/
|
|
/*
|
* This is on the tail page. It is possible that
|
* a write could come in and move the tail page
|
* and write to the next page. That is fine
|
* because we just shorten what is on this page.
|
*/
|
old_index += write_mask;
|
new_index += write_mask;
|
index = local_cmpxchg(&bpage->write, old_index, new_index);
|
if (index == old_index) {
|
/* update counters */
|
local_sub(event_length, &cpu_buffer->entries_bytes);
|
return 1;
|
}
|
}
|
|
/* could not discard */
|
return 0;
|
}
|
|
static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
local_inc(&cpu_buffer->committing);
|
local_inc(&cpu_buffer->commits);
|
}
|
|
static __always_inline void
|
rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
unsigned long max_count;
|
|
/*
|
* We only race with interrupts and NMIs on this CPU.
|
* If we own the commit event, then we can commit
|
* all others that interrupted us, since the interruptions
|
* are in stack format (they finish before they come
|
* back to us). This allows us to do a simple loop to
|
* assign the commit to the tail.
|
*/
|
again:
|
max_count = cpu_buffer->nr_pages * 100;
|
|
while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
|
if (RB_WARN_ON(cpu_buffer, !(--max_count)))
|
return;
|
if (RB_WARN_ON(cpu_buffer,
|
rb_is_reader_page(cpu_buffer->tail_page)))
|
return;
|
local_set(&cpu_buffer->commit_page->page->commit,
|
rb_page_write(cpu_buffer->commit_page));
|
rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
|
/* add barrier to keep gcc from optimizing too much */
|
barrier();
|
}
|
while (rb_commit_index(cpu_buffer) !=
|
rb_page_write(cpu_buffer->commit_page)) {
|
|
local_set(&cpu_buffer->commit_page->page->commit,
|
rb_page_write(cpu_buffer->commit_page));
|
RB_WARN_ON(cpu_buffer,
|
local_read(&cpu_buffer->commit_page->page->commit) &
|
~RB_WRITE_MASK);
|
barrier();
|
}
|
|
/* again, keep gcc from optimizing */
|
barrier();
|
|
/*
|
* If an interrupt came in just after the first while loop
|
* and pushed the tail page forward, we will be left with
|
* a dangling commit that will never go forward.
|
*/
|
if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
|
goto again;
|
}
|
|
static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
unsigned long commits;
|
|
if (RB_WARN_ON(cpu_buffer,
|
!local_read(&cpu_buffer->committing)))
|
return;
|
|
again:
|
commits = local_read(&cpu_buffer->commits);
|
/* synchronize with interrupts */
|
barrier();
|
if (local_read(&cpu_buffer->committing) == 1)
|
rb_set_commit_to_write(cpu_buffer);
|
|
local_dec(&cpu_buffer->committing);
|
|
/* synchronize with interrupts */
|
barrier();
|
|
/*
|
* Need to account for interrupts coming in between the
|
* updating of the commit page and the clearing of the
|
* committing counter.
|
*/
|
if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
|
!local_read(&cpu_buffer->committing)) {
|
local_inc(&cpu_buffer->committing);
|
goto again;
|
}
|
}
|
|
static inline void rb_event_discard(struct ring_buffer_event *event)
|
{
|
if (extended_time(event))
|
event = skip_time_extend(event);
|
|
/* array[0] holds the actual length for the discarded event */
|
event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
|
event->type_len = RINGBUF_TYPE_PADDING;
|
/* time delta must be non zero */
|
if (!event->time_delta)
|
event->time_delta = 1;
|
}
|
|
static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
|
struct ring_buffer_event *event)
|
{
|
local_inc(&cpu_buffer->entries);
|
rb_end_commit(cpu_buffer);
|
}
|
|
static __always_inline void
|
rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
if (buffer->irq_work.waiters_pending) {
|
buffer->irq_work.waiters_pending = false;
|
/* irq_work_queue() supplies it's own memory barriers */
|
irq_work_queue(&buffer->irq_work.work);
|
}
|
|
if (cpu_buffer->irq_work.waiters_pending) {
|
cpu_buffer->irq_work.waiters_pending = false;
|
/* irq_work_queue() supplies it's own memory barriers */
|
irq_work_queue(&cpu_buffer->irq_work.work);
|
}
|
|
if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
|
return;
|
|
if (cpu_buffer->reader_page == cpu_buffer->commit_page)
|
return;
|
|
if (!cpu_buffer->irq_work.full_waiters_pending)
|
return;
|
|
cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
|
|
if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
|
return;
|
|
cpu_buffer->irq_work.wakeup_full = true;
|
cpu_buffer->irq_work.full_waiters_pending = false;
|
/* irq_work_queue() supplies it's own memory barriers */
|
irq_work_queue(&cpu_buffer->irq_work.work);
|
}
|
|
/*
|
* The lock and unlock are done within a preempt disable section.
|
* The current_context per_cpu variable can only be modified
|
* by the current task between lock and unlock. But it can
|
* be modified more than once via an interrupt. To pass this
|
* information from the lock to the unlock without having to
|
* access the 'in_interrupt()' functions again (which do show
|
* a bit of overhead in something as critical as function tracing,
|
* we use a bitmask trick.
|
*
|
* bit 1 = NMI context
|
* bit 2 = IRQ context
|
* bit 3 = SoftIRQ context
|
* bit 4 = normal context.
|
*
|
* This works because this is the order of contexts that can
|
* preempt other contexts. A SoftIRQ never preempts an IRQ
|
* context.
|
*
|
* When the context is determined, the corresponding bit is
|
* checked and set (if it was set, then a recursion of that context
|
* happened).
|
*
|
* On unlock, we need to clear this bit. To do so, just subtract
|
* 1 from the current_context and AND it to itself.
|
*
|
* (binary)
|
* 101 - 1 = 100
|
* 101 & 100 = 100 (clearing bit zero)
|
*
|
* 1010 - 1 = 1001
|
* 1010 & 1001 = 1000 (clearing bit 1)
|
*
|
* The least significant bit can be cleared this way, and it
|
* just so happens that it is the same bit corresponding to
|
* the current context.
|
*
|
* Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
|
* is set when a recursion is detected at the current context, and if
|
* the TRANSITION bit is already set, it will fail the recursion.
|
* This is needed because there's a lag between the changing of
|
* interrupt context and updating the preempt count. In this case,
|
* a false positive will be found. To handle this, one extra recursion
|
* is allowed, and this is done by the TRANSITION bit. If the TRANSITION
|
* bit is already set, then it is considered a recursion and the function
|
* ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
|
*
|
* On the trace_recursive_unlock(), the TRANSITION bit will be the first
|
* to be cleared. Even if it wasn't the context that set it. That is,
|
* if an interrupt comes in while NORMAL bit is set and the ring buffer
|
* is called before preempt_count() is updated, since the check will
|
* be on the NORMAL bit, the TRANSITION bit will then be set. If an
|
* NMI then comes in, it will set the NMI bit, but when the NMI code
|
* does the trace_recursive_unlock() it will clear the TRANSTION bit
|
* and leave the NMI bit set. But this is fine, because the interrupt
|
* code that set the TRANSITION bit will then clear the NMI bit when it
|
* calls trace_recursive_unlock(). If another NMI comes in, it will
|
* set the TRANSITION bit and continue.
|
*
|
* Note: The TRANSITION bit only handles a single transition between context.
|
*/
|
|
static __always_inline int
|
trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
unsigned int val = cpu_buffer->current_context;
|
unsigned long pc = preempt_count();
|
int bit;
|
|
if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
|
bit = RB_CTX_NORMAL;
|
else
|
bit = pc & NMI_MASK ? RB_CTX_NMI :
|
pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
|
|
if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
|
/*
|
* It is possible that this was called by transitioning
|
* between interrupt context, and preempt_count() has not
|
* been updated yet. In this case, use the TRANSITION bit.
|
*/
|
bit = RB_CTX_TRANSITION;
|
if (val & (1 << (bit + cpu_buffer->nest)))
|
return 1;
|
}
|
|
val |= (1 << (bit + cpu_buffer->nest));
|
cpu_buffer->current_context = val;
|
|
return 0;
|
}
|
|
static __always_inline void
|
trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
cpu_buffer->current_context &=
|
cpu_buffer->current_context - (1 << cpu_buffer->nest);
|
}
|
|
/* The recursive locking above uses 5 bits */
|
#define NESTED_BITS 5
|
|
/**
|
* ring_buffer_nest_start - Allow to trace while nested
|
* @buffer: The ring buffer to modify
|
*
|
* The ring buffer has a safety mechanism to prevent recursion.
|
* But there may be a case where a trace needs to be done while
|
* tracing something else. In this case, calling this function
|
* will allow this function to nest within a currently active
|
* ring_buffer_lock_reserve().
|
*
|
* Call this function before calling another ring_buffer_lock_reserve() and
|
* call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
|
*/
|
void ring_buffer_nest_start(struct trace_buffer *buffer)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
int cpu;
|
|
/* Enabled by ring_buffer_nest_end() */
|
preempt_disable_notrace();
|
cpu = raw_smp_processor_id();
|
cpu_buffer = buffer->buffers[cpu];
|
/* This is the shift value for the above recursive locking */
|
cpu_buffer->nest += NESTED_BITS;
|
}
|
|
/**
|
* ring_buffer_nest_end - Allow to trace while nested
|
* @buffer: The ring buffer to modify
|
*
|
* Must be called after ring_buffer_nest_start() and after the
|
* ring_buffer_unlock_commit().
|
*/
|
void ring_buffer_nest_end(struct trace_buffer *buffer)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
int cpu;
|
|
/* disabled by ring_buffer_nest_start() */
|
cpu = raw_smp_processor_id();
|
cpu_buffer = buffer->buffers[cpu];
|
/* This is the shift value for the above recursive locking */
|
cpu_buffer->nest -= NESTED_BITS;
|
preempt_enable_notrace();
|
}
|
|
/**
|
* ring_buffer_unlock_commit - commit a reserved
|
* @buffer: The buffer to commit to
|
* @event: The event pointer to commit.
|
*
|
* This commits the data to the ring buffer, and releases any locks held.
|
*
|
* Must be paired with ring_buffer_lock_reserve.
|
*/
|
int ring_buffer_unlock_commit(struct trace_buffer *buffer,
|
struct ring_buffer_event *event)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
int cpu = raw_smp_processor_id();
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
rb_commit(cpu_buffer, event);
|
|
rb_wakeups(buffer, cpu_buffer);
|
|
trace_recursive_unlock(cpu_buffer);
|
|
preempt_enable_notrace();
|
|
return 0;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
|
|
static struct ring_buffer_event *
|
__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
|
struct rb_event_info *info)
|
{
|
struct ring_buffer_event *event;
|
struct buffer_page *tail_page;
|
unsigned long tail, write, w;
|
bool a_ok;
|
bool b_ok;
|
|
/* Don't let the compiler play games with cpu_buffer->tail_page */
|
tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
|
|
/*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
|
barrier();
|
b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
|
a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
|
barrier();
|
info->ts = rb_time_stamp(cpu_buffer->buffer);
|
|
if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
|
info->delta = info->ts;
|
} else {
|
/*
|
* If interrupting an event time update, we may need an
|
* absolute timestamp.
|
* Don't bother if this is the start of a new page (w == 0).
|
*/
|
if (unlikely(!a_ok || !b_ok || (info->before != info->after && w))) {
|
info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
|
info->length += RB_LEN_TIME_EXTEND;
|
} else {
|
info->delta = info->ts - info->after;
|
if (unlikely(test_time_stamp(info->delta))) {
|
info->add_timestamp |= RB_ADD_STAMP_EXTEND;
|
info->length += RB_LEN_TIME_EXTEND;
|
}
|
}
|
}
|
|
/*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
|
|
/*C*/ write = local_add_return(info->length, &tail_page->write);
|
|
/* set write to only the index of the write */
|
write &= RB_WRITE_MASK;
|
|
tail = write - info->length;
|
|
/* See if we shot pass the end of this buffer page */
|
if (unlikely(write > BUF_PAGE_SIZE)) {
|
/* before and after may now different, fix it up*/
|
b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
|
a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
|
if (a_ok && b_ok && info->before != info->after)
|
(void)rb_time_cmpxchg(&cpu_buffer->before_stamp,
|
info->before, info->after);
|
return rb_move_tail(cpu_buffer, tail, info);
|
}
|
|
if (likely(tail == w)) {
|
u64 save_before;
|
bool s_ok;
|
|
/* Nothing interrupted us between A and C */
|
/*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
|
barrier();
|
/*E*/ s_ok = rb_time_read(&cpu_buffer->before_stamp, &save_before);
|
RB_WARN_ON(cpu_buffer, !s_ok);
|
if (likely(!(info->add_timestamp &
|
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
|
/* This did not interrupt any time update */
|
info->delta = info->ts - info->after;
|
else
|
/* Just use full timestamp for inerrupting event */
|
info->delta = info->ts;
|
barrier();
|
if (unlikely(info->ts != save_before)) {
|
/* SLOW PATH - Interrupted between C and E */
|
|
a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
|
RB_WARN_ON(cpu_buffer, !a_ok);
|
|
/* Write stamp must only go forward */
|
if (save_before > info->after) {
|
/*
|
* We do not care about the result, only that
|
* it gets updated atomically.
|
*/
|
(void)rb_time_cmpxchg(&cpu_buffer->write_stamp,
|
info->after, save_before);
|
}
|
}
|
} else {
|
u64 ts;
|
/* SLOW PATH - Interrupted between A and C */
|
a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
|
/* Was interrupted before here, write_stamp must be valid */
|
RB_WARN_ON(cpu_buffer, !a_ok);
|
ts = rb_time_stamp(cpu_buffer->buffer);
|
barrier();
|
/*E*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
|
info->after < ts &&
|
rb_time_cmpxchg(&cpu_buffer->write_stamp,
|
info->after, ts)) {
|
/* Nothing came after this event between C and E */
|
info->delta = ts - info->after;
|
info->ts = ts;
|
} else {
|
/*
|
* Interrupted beween C and E:
|
* Lost the previous events time stamp. Just set the
|
* delta to zero, and this will be the same time as
|
* the event this event interrupted. And the events that
|
* came after this will still be correct (as they would
|
* have built their delta on the previous event.
|
*/
|
info->delta = 0;
|
}
|
info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
|
}
|
|
/*
|
* If this is the first commit on the page, then it has the same
|
* timestamp as the page itself.
|
*/
|
if (unlikely(!tail && !(info->add_timestamp &
|
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
|
info->delta = 0;
|
|
/* We reserved something on the buffer */
|
|
event = __rb_page_index(tail_page, tail);
|
rb_update_event(cpu_buffer, event, info);
|
|
local_inc(&tail_page->entries);
|
|
/*
|
* If this is the first commit on the page, then update
|
* its timestamp.
|
*/
|
if (unlikely(!tail))
|
tail_page->page->time_stamp = info->ts;
|
|
/* account for these added bytes */
|
local_add(info->length, &cpu_buffer->entries_bytes);
|
|
return event;
|
}
|
|
static __always_inline struct ring_buffer_event *
|
rb_reserve_next_event(struct trace_buffer *buffer,
|
struct ring_buffer_per_cpu *cpu_buffer,
|
unsigned long length)
|
{
|
struct ring_buffer_event *event;
|
struct rb_event_info info;
|
int nr_loops = 0;
|
int add_ts_default;
|
|
rb_start_commit(cpu_buffer);
|
/* The commit page can not change after this */
|
|
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
|
/*
|
* Due to the ability to swap a cpu buffer from a buffer
|
* it is possible it was swapped before we committed.
|
* (committing stops a swap). We check for it here and
|
* if it happened, we have to fail the write.
|
*/
|
barrier();
|
if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
|
local_dec(&cpu_buffer->committing);
|
local_dec(&cpu_buffer->commits);
|
return NULL;
|
}
|
#endif
|
|
info.length = rb_calculate_event_length(length);
|
|
if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
|
add_ts_default = RB_ADD_STAMP_ABSOLUTE;
|
info.length += RB_LEN_TIME_EXTEND;
|
} else {
|
add_ts_default = RB_ADD_STAMP_NONE;
|
}
|
|
again:
|
info.add_timestamp = add_ts_default;
|
info.delta = 0;
|
|
/*
|
* We allow for interrupts to reenter here and do a trace.
|
* If one does, it will cause this original code to loop
|
* back here. Even with heavy interrupts happening, this
|
* should only happen a few times in a row. If this happens
|
* 1000 times in a row, there must be either an interrupt
|
* storm or we have something buggy.
|
* Bail!
|
*/
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
|
goto out_fail;
|
|
event = __rb_reserve_next(cpu_buffer, &info);
|
|
if (unlikely(PTR_ERR(event) == -EAGAIN)) {
|
if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
|
info.length -= RB_LEN_TIME_EXTEND;
|
goto again;
|
}
|
|
if (likely(event))
|
return event;
|
out_fail:
|
rb_end_commit(cpu_buffer);
|
return NULL;
|
}
|
|
/**
|
* ring_buffer_lock_reserve - reserve a part of the buffer
|
* @buffer: the ring buffer to reserve from
|
* @length: the length of the data to reserve (excluding event header)
|
*
|
* Returns a reserved event on the ring buffer to copy directly to.
|
* The user of this interface will need to get the body to write into
|
* and can use the ring_buffer_event_data() interface.
|
*
|
* The length is the length of the data needed, not the event length
|
* which also includes the event header.
|
*
|
* Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
|
* If NULL is returned, then nothing has been allocated or locked.
|
*/
|
struct ring_buffer_event *
|
ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
struct ring_buffer_event *event;
|
int cpu;
|
|
/* If we are tracing schedule, we don't want to recurse */
|
preempt_disable_notrace();
|
|
if (unlikely(atomic_read(&buffer->record_disabled)))
|
goto out;
|
|
cpu = raw_smp_processor_id();
|
|
if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
|
goto out;
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
|
goto out;
|
|
if (unlikely(length > BUF_MAX_DATA_SIZE))
|
goto out;
|
|
if (unlikely(trace_recursive_lock(cpu_buffer)))
|
goto out;
|
|
event = rb_reserve_next_event(buffer, cpu_buffer, length);
|
if (!event)
|
goto out_unlock;
|
|
return event;
|
|
out_unlock:
|
trace_recursive_unlock(cpu_buffer);
|
out:
|
preempt_enable_notrace();
|
return NULL;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
|
|
/*
|
* Decrement the entries to the page that an event is on.
|
* The event does not even need to exist, only the pointer
|
* to the page it is on. This may only be called before the commit
|
* takes place.
|
*/
|
static inline void
|
rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
|
struct ring_buffer_event *event)
|
{
|
unsigned long addr = (unsigned long)event;
|
struct buffer_page *bpage = cpu_buffer->commit_page;
|
struct buffer_page *start;
|
|
addr &= PAGE_MASK;
|
|
/* Do the likely case first */
|
if (likely(bpage->page == (void *)addr)) {
|
local_dec(&bpage->entries);
|
return;
|
}
|
|
/*
|
* Because the commit page may be on the reader page we
|
* start with the next page and check the end loop there.
|
*/
|
rb_inc_page(cpu_buffer, &bpage);
|
start = bpage;
|
do {
|
if (bpage->page == (void *)addr) {
|
local_dec(&bpage->entries);
|
return;
|
}
|
rb_inc_page(cpu_buffer, &bpage);
|
} while (bpage != start);
|
|
/* commit not part of this buffer?? */
|
RB_WARN_ON(cpu_buffer, 1);
|
}
|
|
/**
|
* ring_buffer_commit_discard - discard an event that has not been committed
|
* @buffer: the ring buffer
|
* @event: non committed event to discard
|
*
|
* Sometimes an event that is in the ring buffer needs to be ignored.
|
* This function lets the user discard an event in the ring buffer
|
* and then that event will not be read later.
|
*
|
* This function only works if it is called before the item has been
|
* committed. It will try to free the event from the ring buffer
|
* if another event has not been added behind it.
|
*
|
* If another event has been added behind it, it will set the event
|
* up as discarded, and perform the commit.
|
*
|
* If this function is called, do not call ring_buffer_unlock_commit on
|
* the event.
|
*/
|
void ring_buffer_discard_commit(struct trace_buffer *buffer,
|
struct ring_buffer_event *event)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
int cpu;
|
|
/* The event is discarded regardless */
|
rb_event_discard(event);
|
|
cpu = smp_processor_id();
|
cpu_buffer = buffer->buffers[cpu];
|
|
/*
|
* This must only be called if the event has not been
|
* committed yet. Thus we can assume that preemption
|
* is still disabled.
|
*/
|
RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
|
|
rb_decrement_entry(cpu_buffer, event);
|
if (rb_try_to_discard(cpu_buffer, event))
|
goto out;
|
|
out:
|
rb_end_commit(cpu_buffer);
|
|
trace_recursive_unlock(cpu_buffer);
|
|
preempt_enable_notrace();
|
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
|
|
/**
|
* ring_buffer_write - write data to the buffer without reserving
|
* @buffer: The ring buffer to write to.
|
* @length: The length of the data being written (excluding the event header)
|
* @data: The data to write to the buffer.
|
*
|
* This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
|
* one function. If you already have the data to write to the buffer, it
|
* may be easier to simply call this function.
|
*
|
* Note, like ring_buffer_lock_reserve, the length is the length of the data
|
* and not the length of the event which would hold the header.
|
*/
|
int ring_buffer_write(struct trace_buffer *buffer,
|
unsigned long length,
|
void *data)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
struct ring_buffer_event *event;
|
void *body;
|
int ret = -EBUSY;
|
int cpu;
|
|
preempt_disable_notrace();
|
|
if (atomic_read(&buffer->record_disabled))
|
goto out;
|
|
cpu = raw_smp_processor_id();
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
goto out;
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
if (atomic_read(&cpu_buffer->record_disabled))
|
goto out;
|
|
if (length > BUF_MAX_DATA_SIZE)
|
goto out;
|
|
if (unlikely(trace_recursive_lock(cpu_buffer)))
|
goto out;
|
|
event = rb_reserve_next_event(buffer, cpu_buffer, length);
|
if (!event)
|
goto out_unlock;
|
|
body = rb_event_data(event);
|
|
memcpy(body, data, length);
|
|
rb_commit(cpu_buffer, event);
|
|
rb_wakeups(buffer, cpu_buffer);
|
|
ret = 0;
|
|
out_unlock:
|
trace_recursive_unlock(cpu_buffer);
|
|
out:
|
preempt_enable_notrace();
|
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_write);
|
|
static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
struct buffer_page *reader = cpu_buffer->reader_page;
|
struct buffer_page *head = rb_set_head_page(cpu_buffer);
|
struct buffer_page *commit = cpu_buffer->commit_page;
|
|
/* In case of error, head will be NULL */
|
if (unlikely(!head))
|
return true;
|
|
/* Reader should exhaust content in reader page */
|
if (reader->read != rb_page_commit(reader))
|
return false;
|
|
/*
|
* If writers are committing on the reader page, knowing all
|
* committed content has been read, the ring buffer is empty.
|
*/
|
if (commit == reader)
|
return true;
|
|
/*
|
* If writers are committing on a page other than reader page
|
* and head page, there should always be content to read.
|
*/
|
if (commit != head)
|
return false;
|
|
/*
|
* Writers are committing on the head page, we just need
|
* to care about there're committed data, and the reader will
|
* swap reader page with head page when it is to read data.
|
*/
|
return rb_page_commit(commit) == 0;
|
}
|
|
/**
|
* ring_buffer_record_disable - stop all writes into the buffer
|
* @buffer: The ring buffer to stop writes to.
|
*
|
* This prevents all writes to the buffer. Any attempt to write
|
* to the buffer after this will fail and return NULL.
|
*
|
* The caller should call synchronize_rcu() after this.
|
*/
|
void ring_buffer_record_disable(struct trace_buffer *buffer)
|
{
|
atomic_inc(&buffer->record_disabled);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
|
|
/**
|
* ring_buffer_record_enable - enable writes to the buffer
|
* @buffer: The ring buffer to enable writes
|
*
|
* Note, multiple disables will need the same number of enables
|
* to truly enable the writing (much like preempt_disable).
|
*/
|
void ring_buffer_record_enable(struct trace_buffer *buffer)
|
{
|
atomic_dec(&buffer->record_disabled);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
|
|
/**
|
* ring_buffer_record_off - stop all writes into the buffer
|
* @buffer: The ring buffer to stop writes to.
|
*
|
* This prevents all writes to the buffer. Any attempt to write
|
* to the buffer after this will fail and return NULL.
|
*
|
* This is different than ring_buffer_record_disable() as
|
* it works like an on/off switch, where as the disable() version
|
* must be paired with a enable().
|
*/
|
void ring_buffer_record_off(struct trace_buffer *buffer)
|
{
|
unsigned int rd;
|
unsigned int new_rd;
|
|
do {
|
rd = atomic_read(&buffer->record_disabled);
|
new_rd = rd | RB_BUFFER_OFF;
|
} while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_record_off);
|
|
/**
|
* ring_buffer_record_on - restart writes into the buffer
|
* @buffer: The ring buffer to start writes to.
|
*
|
* This enables all writes to the buffer that was disabled by
|
* ring_buffer_record_off().
|
*
|
* This is different than ring_buffer_record_enable() as
|
* it works like an on/off switch, where as the enable() version
|
* must be paired with a disable().
|
*/
|
void ring_buffer_record_on(struct trace_buffer *buffer)
|
{
|
unsigned int rd;
|
unsigned int new_rd;
|
|
do {
|
rd = atomic_read(&buffer->record_disabled);
|
new_rd = rd & ~RB_BUFFER_OFF;
|
} while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_record_on);
|
|
/**
|
* ring_buffer_record_is_on - return true if the ring buffer can write
|
* @buffer: The ring buffer to see if write is enabled
|
*
|
* Returns true if the ring buffer is in a state that it accepts writes.
|
*/
|
bool ring_buffer_record_is_on(struct trace_buffer *buffer)
|
{
|
return !atomic_read(&buffer->record_disabled);
|
}
|
|
/**
|
* ring_buffer_record_is_set_on - return true if the ring buffer is set writable
|
* @buffer: The ring buffer to see if write is set enabled
|
*
|
* Returns true if the ring buffer is set writable by ring_buffer_record_on().
|
* Note that this does NOT mean it is in a writable state.
|
*
|
* It may return true when the ring buffer has been disabled by
|
* ring_buffer_record_disable(), as that is a temporary disabling of
|
* the ring buffer.
|
*/
|
bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
|
{
|
return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
|
}
|
|
/**
|
* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
|
* @buffer: The ring buffer to stop writes to.
|
* @cpu: The CPU buffer to stop
|
*
|
* This prevents all writes to the buffer. Any attempt to write
|
* to the buffer after this will fail and return NULL.
|
*
|
* The caller should call synchronize_rcu() after this.
|
*/
|
void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return;
|
|
cpu_buffer = buffer->buffers[cpu];
|
atomic_inc(&cpu_buffer->record_disabled);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
|
|
/**
|
* ring_buffer_record_enable_cpu - enable writes to the buffer
|
* @buffer: The ring buffer to enable writes
|
* @cpu: The CPU to enable.
|
*
|
* Note, multiple disables will need the same number of enables
|
* to truly enable the writing (much like preempt_disable).
|
*/
|
void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return;
|
|
cpu_buffer = buffer->buffers[cpu];
|
atomic_dec(&cpu_buffer->record_disabled);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
|
|
/*
|
* The total entries in the ring buffer is the running counter
|
* of entries entered into the ring buffer, minus the sum of
|
* the entries read from the ring buffer and the number of
|
* entries that were overwritten.
|
*/
|
static inline unsigned long
|
rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
return local_read(&cpu_buffer->entries) -
|
(local_read(&cpu_buffer->overrun) + cpu_buffer->read);
|
}
|
|
/**
|
* ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
|
* @buffer: The ring buffer
|
* @cpu: The per CPU buffer to read from.
|
*/
|
u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
|
{
|
unsigned long flags;
|
struct ring_buffer_per_cpu *cpu_buffer;
|
struct buffer_page *bpage;
|
u64 ret = 0;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return 0;
|
|
cpu_buffer = buffer->buffers[cpu];
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
/*
|
* if the tail is on reader_page, oldest time stamp is on the reader
|
* page
|
*/
|
if (cpu_buffer->tail_page == cpu_buffer->reader_page)
|
bpage = cpu_buffer->reader_page;
|
else
|
bpage = rb_set_head_page(cpu_buffer);
|
if (bpage)
|
ret = bpage->page->time_stamp;
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
|
|
/**
|
* ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
|
* @buffer: The ring buffer
|
* @cpu: The per CPU buffer to read from.
|
*/
|
unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
unsigned long ret;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return 0;
|
|
cpu_buffer = buffer->buffers[cpu];
|
ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
|
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
|
|
/**
|
* ring_buffer_entries_cpu - get the number of entries in a cpu buffer
|
* @buffer: The ring buffer
|
* @cpu: The per CPU buffer to get the entries from.
|
*/
|
unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return 0;
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
return rb_num_of_entries(cpu_buffer);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
|
|
/**
|
* ring_buffer_overrun_cpu - get the number of overruns caused by the ring
|
* buffer wrapping around (only if RB_FL_OVERWRITE is on).
|
* @buffer: The ring buffer
|
* @cpu: The per CPU buffer to get the number of overruns from
|
*/
|
unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
unsigned long ret;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return 0;
|
|
cpu_buffer = buffer->buffers[cpu];
|
ret = local_read(&cpu_buffer->overrun);
|
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
|
|
/**
|
* ring_buffer_commit_overrun_cpu - get the number of overruns caused by
|
* commits failing due to the buffer wrapping around while there are uncommitted
|
* events, such as during an interrupt storm.
|
* @buffer: The ring buffer
|
* @cpu: The per CPU buffer to get the number of overruns from
|
*/
|
unsigned long
|
ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
unsigned long ret;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return 0;
|
|
cpu_buffer = buffer->buffers[cpu];
|
ret = local_read(&cpu_buffer->commit_overrun);
|
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
|
|
/**
|
* ring_buffer_dropped_events_cpu - get the number of dropped events caused by
|
* the ring buffer filling up (only if RB_FL_OVERWRITE is off).
|
* @buffer: The ring buffer
|
* @cpu: The per CPU buffer to get the number of overruns from
|
*/
|
unsigned long
|
ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
unsigned long ret;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return 0;
|
|
cpu_buffer = buffer->buffers[cpu];
|
ret = local_read(&cpu_buffer->dropped_events);
|
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
|
|
/**
|
* ring_buffer_read_events_cpu - get the number of events successfully read
|
* @buffer: The ring buffer
|
* @cpu: The per CPU buffer to get the number of events read
|
*/
|
unsigned long
|
ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return 0;
|
|
cpu_buffer = buffer->buffers[cpu];
|
return cpu_buffer->read;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
|
|
/**
|
* ring_buffer_entries - get the number of entries in a buffer
|
* @buffer: The ring buffer
|
*
|
* Returns the total number of entries in the ring buffer
|
* (all CPU entries)
|
*/
|
unsigned long ring_buffer_entries(struct trace_buffer *buffer)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
unsigned long entries = 0;
|
int cpu;
|
|
/* if you care about this being correct, lock the buffer */
|
for_each_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
entries += rb_num_of_entries(cpu_buffer);
|
}
|
|
return entries;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_entries);
|
|
/**
|
* ring_buffer_overruns - get the number of overruns in buffer
|
* @buffer: The ring buffer
|
*
|
* Returns the total number of overruns in the ring buffer
|
* (all CPU entries)
|
*/
|
unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
unsigned long overruns = 0;
|
int cpu;
|
|
/* if you care about this being correct, lock the buffer */
|
for_each_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
overruns += local_read(&cpu_buffer->overrun);
|
}
|
|
return overruns;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_overruns);
|
|
static void rb_iter_reset(struct ring_buffer_iter *iter)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
/* Iterator usage is expected to have record disabled */
|
iter->head_page = cpu_buffer->reader_page;
|
iter->head = cpu_buffer->reader_page->read;
|
iter->next_event = iter->head;
|
|
iter->cache_reader_page = iter->head_page;
|
iter->cache_read = cpu_buffer->read;
|
|
if (iter->head) {
|
iter->read_stamp = cpu_buffer->read_stamp;
|
iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
|
} else {
|
iter->read_stamp = iter->head_page->page->time_stamp;
|
iter->page_stamp = iter->read_stamp;
|
}
|
}
|
|
/**
|
* ring_buffer_iter_reset - reset an iterator
|
* @iter: The iterator to reset
|
*
|
* Resets the iterator, so that it will start from the beginning
|
* again.
|
*/
|
void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
unsigned long flags;
|
|
if (!iter)
|
return;
|
|
cpu_buffer = iter->cpu_buffer;
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
rb_iter_reset(iter);
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
|
|
/**
|
* ring_buffer_iter_empty - check if an iterator has no more to read
|
* @iter: The iterator to check
|
*/
|
int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
struct buffer_page *reader;
|
struct buffer_page *head_page;
|
struct buffer_page *commit_page;
|
struct buffer_page *curr_commit_page;
|
unsigned commit;
|
u64 curr_commit_ts;
|
u64 commit_ts;
|
|
cpu_buffer = iter->cpu_buffer;
|
reader = cpu_buffer->reader_page;
|
head_page = cpu_buffer->head_page;
|
commit_page = cpu_buffer->commit_page;
|
commit_ts = commit_page->page->time_stamp;
|
|
/*
|
* When the writer goes across pages, it issues a cmpxchg which
|
* is a mb(), which will synchronize with the rmb here.
|
* (see rb_tail_page_update())
|
*/
|
smp_rmb();
|
commit = rb_page_commit(commit_page);
|
/* We want to make sure that the commit page doesn't change */
|
smp_rmb();
|
|
/* Make sure commit page didn't change */
|
curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
|
curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
|
|
/* If the commit page changed, then there's more data */
|
if (curr_commit_page != commit_page ||
|
curr_commit_ts != commit_ts)
|
return 0;
|
|
/* Still racy, as it may return a false positive, but that's OK */
|
return ((iter->head_page == commit_page && iter->head >= commit) ||
|
(iter->head_page == reader && commit_page == head_page &&
|
head_page->read == commit &&
|
iter->head == rb_page_commit(cpu_buffer->reader_page)));
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
|
|
static void
|
rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
|
struct ring_buffer_event *event)
|
{
|
u64 delta;
|
|
switch (event->type_len) {
|
case RINGBUF_TYPE_PADDING:
|
return;
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
delta = ring_buffer_event_time_stamp(event);
|
cpu_buffer->read_stamp += delta;
|
return;
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
delta = ring_buffer_event_time_stamp(event);
|
cpu_buffer->read_stamp = delta;
|
return;
|
|
case RINGBUF_TYPE_DATA:
|
cpu_buffer->read_stamp += event->time_delta;
|
return;
|
|
default:
|
RB_WARN_ON(cpu_buffer, 1);
|
}
|
return;
|
}
|
|
static void
|
rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
|
struct ring_buffer_event *event)
|
{
|
u64 delta;
|
|
switch (event->type_len) {
|
case RINGBUF_TYPE_PADDING:
|
return;
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
delta = ring_buffer_event_time_stamp(event);
|
iter->read_stamp += delta;
|
return;
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
delta = ring_buffer_event_time_stamp(event);
|
iter->read_stamp = delta;
|
return;
|
|
case RINGBUF_TYPE_DATA:
|
iter->read_stamp += event->time_delta;
|
return;
|
|
default:
|
RB_WARN_ON(iter->cpu_buffer, 1);
|
}
|
return;
|
}
|
|
static struct buffer_page *
|
rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
struct buffer_page *reader = NULL;
|
unsigned long overwrite;
|
unsigned long flags;
|
int nr_loops = 0;
|
int ret;
|
|
local_irq_save(flags);
|
arch_spin_lock(&cpu_buffer->lock);
|
|
again:
|
/*
|
* This should normally only loop twice. But because the
|
* start of the reader inserts an empty page, it causes
|
* a case where we will loop three times. There should be no
|
* reason to loop four times (that I know of).
|
*/
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
|
reader = NULL;
|
goto out;
|
}
|
|
reader = cpu_buffer->reader_page;
|
|
/* If there's more to read, return this page */
|
if (cpu_buffer->reader_page->read < rb_page_size(reader))
|
goto out;
|
|
/* Never should we have an index greater than the size */
|
if (RB_WARN_ON(cpu_buffer,
|
cpu_buffer->reader_page->read > rb_page_size(reader)))
|
goto out;
|
|
/* check if we caught up to the tail */
|
reader = NULL;
|
if (cpu_buffer->commit_page == cpu_buffer->reader_page)
|
goto out;
|
|
/* Don't bother swapping if the ring buffer is empty */
|
if (rb_num_of_entries(cpu_buffer) == 0)
|
goto out;
|
|
/*
|
* Reset the reader page to size zero.
|
*/
|
local_set(&cpu_buffer->reader_page->write, 0);
|
local_set(&cpu_buffer->reader_page->entries, 0);
|
local_set(&cpu_buffer->reader_page->page->commit, 0);
|
cpu_buffer->reader_page->real_end = 0;
|
|
spin:
|
/*
|
* Splice the empty reader page into the list around the head.
|
*/
|
reader = rb_set_head_page(cpu_buffer);
|
if (!reader)
|
goto out;
|
cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
|
cpu_buffer->reader_page->list.prev = reader->list.prev;
|
|
/*
|
* cpu_buffer->pages just needs to point to the buffer, it
|
* has no specific buffer page to point to. Lets move it out
|
* of our way so we don't accidentally swap it.
|
*/
|
cpu_buffer->pages = reader->list.prev;
|
|
/* The reader page will be pointing to the new head */
|
rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
|
|
/*
|
* We want to make sure we read the overruns after we set up our
|
* pointers to the next object. The writer side does a
|
* cmpxchg to cross pages which acts as the mb on the writer
|
* side. Note, the reader will constantly fail the swap
|
* while the writer is updating the pointers, so this
|
* guarantees that the overwrite recorded here is the one we
|
* want to compare with the last_overrun.
|
*/
|
smp_mb();
|
overwrite = local_read(&(cpu_buffer->overrun));
|
|
/*
|
* Here's the tricky part.
|
*
|
* We need to move the pointer past the header page.
|
* But we can only do that if a writer is not currently
|
* moving it. The page before the header page has the
|
* flag bit '1' set if it is pointing to the page we want.
|
* but if the writer is in the process of moving it
|
* than it will be '2' or already moved '0'.
|
*/
|
|
ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
|
|
/*
|
* If we did not convert it, then we must try again.
|
*/
|
if (!ret)
|
goto spin;
|
|
/*
|
* Yay! We succeeded in replacing the page.
|
*
|
* Now make the new head point back to the reader page.
|
*/
|
rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
|
rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
|
|
local_inc(&cpu_buffer->pages_read);
|
|
/* Finally update the reader page to the new head */
|
cpu_buffer->reader_page = reader;
|
cpu_buffer->reader_page->read = 0;
|
|
if (overwrite != cpu_buffer->last_overrun) {
|
cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
|
cpu_buffer->last_overrun = overwrite;
|
}
|
|
goto again;
|
|
out:
|
/* Update the read_stamp on the first event */
|
if (reader && reader->read == 0)
|
cpu_buffer->read_stamp = reader->page->time_stamp;
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
local_irq_restore(flags);
|
|
/*
|
* The writer has preempt disable, wait for it. But not forever
|
* Although, 1 second is pretty much "forever"
|
*/
|
#define USECS_WAIT 1000000
|
for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
|
/* If the write is past the end of page, a writer is still updating it */
|
if (likely(!reader || rb_page_write(reader) <= BUF_PAGE_SIZE))
|
break;
|
|
udelay(1);
|
|
/* Get the latest version of the reader write value */
|
smp_rmb();
|
}
|
|
/* The writer is not moving forward? Something is wrong */
|
if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
|
reader = NULL;
|
|
/*
|
* Make sure we see any padding after the write update
|
* (see rb_reset_tail())
|
*/
|
smp_rmb();
|
|
|
return reader;
|
}
|
|
static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
struct ring_buffer_event *event;
|
struct buffer_page *reader;
|
unsigned length;
|
|
reader = rb_get_reader_page(cpu_buffer);
|
|
/* This function should not be called when buffer is empty */
|
if (RB_WARN_ON(cpu_buffer, !reader))
|
return;
|
|
event = rb_reader_event(cpu_buffer);
|
|
if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
|
cpu_buffer->read++;
|
|
rb_update_read_stamp(cpu_buffer, event);
|
|
length = rb_event_length(event);
|
cpu_buffer->reader_page->read += length;
|
}
|
|
static void rb_advance_iter(struct ring_buffer_iter *iter)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
cpu_buffer = iter->cpu_buffer;
|
|
/* If head == next_event then we need to jump to the next event */
|
if (iter->head == iter->next_event) {
|
/* If the event gets overwritten again, there's nothing to do */
|
if (rb_iter_head_event(iter) == NULL)
|
return;
|
}
|
|
iter->head = iter->next_event;
|
|
/*
|
* Check if we are at the end of the buffer.
|
*/
|
if (iter->next_event >= rb_page_size(iter->head_page)) {
|
/* discarded commits can make the page empty */
|
if (iter->head_page == cpu_buffer->commit_page)
|
return;
|
rb_inc_iter(iter);
|
return;
|
}
|
|
rb_update_iter_read_stamp(iter, iter->event);
|
}
|
|
static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
return cpu_buffer->lost_events;
|
}
|
|
static struct ring_buffer_event *
|
rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
|
unsigned long *lost_events)
|
{
|
struct ring_buffer_event *event;
|
struct buffer_page *reader;
|
int nr_loops = 0;
|
|
if (ts)
|
*ts = 0;
|
again:
|
/*
|
* We repeat when a time extend is encountered.
|
* Since the time extend is always attached to a data event,
|
* we should never loop more than once.
|
* (We never hit the following condition more than twice).
|
*/
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
|
return NULL;
|
|
reader = rb_get_reader_page(cpu_buffer);
|
if (!reader)
|
return NULL;
|
|
event = rb_reader_event(cpu_buffer);
|
|
switch (event->type_len) {
|
case RINGBUF_TYPE_PADDING:
|
if (rb_null_event(event))
|
RB_WARN_ON(cpu_buffer, 1);
|
/*
|
* Because the writer could be discarding every
|
* event it creates (which would probably be bad)
|
* if we were to go back to "again" then we may never
|
* catch up, and will trigger the warn on, or lock
|
* the box. Return the padding, and we will release
|
* the current locks, and try again.
|
*/
|
return event;
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
/* Internal data, OK to advance */
|
rb_advance_reader(cpu_buffer);
|
goto again;
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
if (ts) {
|
*ts = ring_buffer_event_time_stamp(event);
|
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
|
cpu_buffer->cpu, ts);
|
}
|
/* Internal data, OK to advance */
|
rb_advance_reader(cpu_buffer);
|
goto again;
|
|
case RINGBUF_TYPE_DATA:
|
if (ts && !(*ts)) {
|
*ts = cpu_buffer->read_stamp + event->time_delta;
|
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
|
cpu_buffer->cpu, ts);
|
}
|
if (lost_events)
|
*lost_events = rb_lost_events(cpu_buffer);
|
return event;
|
|
default:
|
RB_WARN_ON(cpu_buffer, 1);
|
}
|
|
return NULL;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_peek);
|
|
static struct ring_buffer_event *
|
rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
|
{
|
struct trace_buffer *buffer;
|
struct ring_buffer_per_cpu *cpu_buffer;
|
struct ring_buffer_event *event;
|
int nr_loops = 0;
|
|
if (ts)
|
*ts = 0;
|
|
cpu_buffer = iter->cpu_buffer;
|
buffer = cpu_buffer->buffer;
|
|
/*
|
* Check if someone performed a consuming read to
|
* the buffer. A consuming read invalidates the iterator
|
* and we need to reset the iterator in this case.
|
*/
|
if (unlikely(iter->cache_read != cpu_buffer->read ||
|
iter->cache_reader_page != cpu_buffer->reader_page))
|
rb_iter_reset(iter);
|
|
again:
|
if (ring_buffer_iter_empty(iter))
|
return NULL;
|
|
/*
|
* As the writer can mess with what the iterator is trying
|
* to read, just give up if we fail to get an event after
|
* three tries. The iterator is not as reliable when reading
|
* the ring buffer with an active write as the consumer is.
|
* Do not warn if the three failures is reached.
|
*/
|
if (++nr_loops > 3)
|
return NULL;
|
|
if (rb_per_cpu_empty(cpu_buffer))
|
return NULL;
|
|
if (iter->head >= rb_page_size(iter->head_page)) {
|
rb_inc_iter(iter);
|
goto again;
|
}
|
|
event = rb_iter_head_event(iter);
|
if (!event)
|
goto again;
|
|
switch (event->type_len) {
|
case RINGBUF_TYPE_PADDING:
|
if (rb_null_event(event)) {
|
rb_inc_iter(iter);
|
goto again;
|
}
|
rb_advance_iter(iter);
|
return event;
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
/* Internal data, OK to advance */
|
rb_advance_iter(iter);
|
goto again;
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
if (ts) {
|
*ts = ring_buffer_event_time_stamp(event);
|
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
|
cpu_buffer->cpu, ts);
|
}
|
/* Internal data, OK to advance */
|
rb_advance_iter(iter);
|
goto again;
|
|
case RINGBUF_TYPE_DATA:
|
if (ts && !(*ts)) {
|
*ts = iter->read_stamp + event->time_delta;
|
ring_buffer_normalize_time_stamp(buffer,
|
cpu_buffer->cpu, ts);
|
}
|
return event;
|
|
default:
|
RB_WARN_ON(cpu_buffer, 1);
|
}
|
|
return NULL;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
|
|
static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
if (likely(!in_nmi())) {
|
raw_spin_lock(&cpu_buffer->reader_lock);
|
return true;
|
}
|
|
/*
|
* If an NMI die dumps out the content of the ring buffer
|
* trylock must be used to prevent a deadlock if the NMI
|
* preempted a task that holds the ring buffer locks. If
|
* we get the lock then all is fine, if not, then continue
|
* to do the read, but this can corrupt the ring buffer,
|
* so it must be permanently disabled from future writes.
|
* Reading from NMI is a oneshot deal.
|
*/
|
if (raw_spin_trylock(&cpu_buffer->reader_lock))
|
return true;
|
|
/* Continue without locking, but disable the ring buffer */
|
atomic_inc(&cpu_buffer->record_disabled);
|
return false;
|
}
|
|
static inline void
|
rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
|
{
|
if (likely(locked))
|
raw_spin_unlock(&cpu_buffer->reader_lock);
|
return;
|
}
|
|
/**
|
* ring_buffer_peek - peek at the next event to be read
|
* @buffer: The ring buffer to read
|
* @cpu: The cpu to peak at
|
* @ts: The timestamp counter of this event.
|
* @lost_events: a variable to store if events were lost (may be NULL)
|
*
|
* This will return the event that will be read next, but does
|
* not consume the data.
|
*/
|
struct ring_buffer_event *
|
ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
|
unsigned long *lost_events)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
struct ring_buffer_event *event;
|
unsigned long flags;
|
bool dolock;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return NULL;
|
|
again:
|
local_irq_save(flags);
|
dolock = rb_reader_lock(cpu_buffer);
|
event = rb_buffer_peek(cpu_buffer, ts, lost_events);
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
rb_advance_reader(cpu_buffer);
|
rb_reader_unlock(cpu_buffer, dolock);
|
local_irq_restore(flags);
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
goto again;
|
|
return event;
|
}
|
|
/** ring_buffer_iter_dropped - report if there are dropped events
|
* @iter: The ring buffer iterator
|
*
|
* Returns true if there was dropped events since the last peek.
|
*/
|
bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
|
{
|
bool ret = iter->missed_events != 0;
|
|
iter->missed_events = 0;
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
|
|
/**
|
* ring_buffer_iter_peek - peek at the next event to be read
|
* @iter: The ring buffer iterator
|
* @ts: The timestamp counter of this event.
|
*
|
* This will return the event that will be read next, but does
|
* not increment the iterator.
|
*/
|
struct ring_buffer_event *
|
ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
struct ring_buffer_event *event;
|
unsigned long flags;
|
|
again:
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
event = rb_iter_peek(iter, ts);
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
goto again;
|
|
return event;
|
}
|
|
/**
|
* ring_buffer_consume - return an event and consume it
|
* @buffer: The ring buffer to get the next event from
|
* @cpu: the cpu to read the buffer from
|
* @ts: a variable to store the timestamp (may be NULL)
|
* @lost_events: a variable to store if events were lost (may be NULL)
|
*
|
* Returns the next event in the ring buffer, and that event is consumed.
|
* Meaning, that sequential reads will keep returning a different event,
|
* and eventually empty the ring buffer if the producer is slower.
|
*/
|
struct ring_buffer_event *
|
ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
|
unsigned long *lost_events)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
struct ring_buffer_event *event = NULL;
|
unsigned long flags;
|
bool dolock;
|
|
again:
|
/* might be called in atomic */
|
preempt_disable();
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
goto out;
|
|
cpu_buffer = buffer->buffers[cpu];
|
local_irq_save(flags);
|
dolock = rb_reader_lock(cpu_buffer);
|
|
event = rb_buffer_peek(cpu_buffer, ts, lost_events);
|
if (event) {
|
cpu_buffer->lost_events = 0;
|
rb_advance_reader(cpu_buffer);
|
}
|
|
rb_reader_unlock(cpu_buffer, dolock);
|
local_irq_restore(flags);
|
|
out:
|
preempt_enable();
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
goto again;
|
|
return event;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_consume);
|
|
/**
|
* ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
|
* @buffer: The ring buffer to read from
|
* @cpu: The cpu buffer to iterate over
|
* @flags: gfp flags to use for memory allocation
|
*
|
* This performs the initial preparations necessary to iterate
|
* through the buffer. Memory is allocated, buffer recording
|
* is disabled, and the iterator pointer is returned to the caller.
|
*
|
* Disabling buffer recording prevents the reading from being
|
* corrupted. This is not a consuming read, so a producer is not
|
* expected.
|
*
|
* After a sequence of ring_buffer_read_prepare calls, the user is
|
* expected to make at least one call to ring_buffer_read_prepare_sync.
|
* Afterwards, ring_buffer_read_start is invoked to get things going
|
* for real.
|
*
|
* This overall must be paired with ring_buffer_read_finish.
|
*/
|
struct ring_buffer_iter *
|
ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
struct ring_buffer_iter *iter;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return NULL;
|
|
iter = kzalloc(sizeof(*iter), flags);
|
if (!iter)
|
return NULL;
|
|
iter->event = kmalloc(BUF_MAX_DATA_SIZE, flags);
|
if (!iter->event) {
|
kfree(iter);
|
return NULL;
|
}
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
iter->cpu_buffer = cpu_buffer;
|
|
atomic_inc(&cpu_buffer->resize_disabled);
|
|
return iter;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
|
|
/**
|
* ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
|
*
|
* All previously invoked ring_buffer_read_prepare calls to prepare
|
* iterators will be synchronized. Afterwards, read_buffer_read_start
|
* calls on those iterators are allowed.
|
*/
|
void
|
ring_buffer_read_prepare_sync(void)
|
{
|
synchronize_rcu();
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
|
|
/**
|
* ring_buffer_read_start - start a non consuming read of the buffer
|
* @iter: The iterator returned by ring_buffer_read_prepare
|
*
|
* This finalizes the startup of an iteration through the buffer.
|
* The iterator comes from a call to ring_buffer_read_prepare and
|
* an intervening ring_buffer_read_prepare_sync must have been
|
* performed.
|
*
|
* Must be paired with ring_buffer_read_finish.
|
*/
|
void
|
ring_buffer_read_start(struct ring_buffer_iter *iter)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
unsigned long flags;
|
|
if (!iter)
|
return;
|
|
cpu_buffer = iter->cpu_buffer;
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
arch_spin_lock(&cpu_buffer->lock);
|
rb_iter_reset(iter);
|
arch_spin_unlock(&cpu_buffer->lock);
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_read_start);
|
|
/**
|
* ring_buffer_read_finish - finish reading the iterator of the buffer
|
* @iter: The iterator retrieved by ring_buffer_start
|
*
|
* This re-enables the recording to the buffer, and frees the
|
* iterator.
|
*/
|
void
|
ring_buffer_read_finish(struct ring_buffer_iter *iter)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
unsigned long flags;
|
|
/*
|
* Ring buffer is disabled from recording, here's a good place
|
* to check the integrity of the ring buffer.
|
* Must prevent readers from trying to read, as the check
|
* clears the HEAD page and readers require it.
|
*/
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
rb_check_pages(cpu_buffer);
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
atomic_dec(&cpu_buffer->resize_disabled);
|
kfree(iter->event);
|
kfree(iter);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
|
|
/**
|
* ring_buffer_iter_advance - advance the iterator to the next location
|
* @iter: The ring buffer iterator
|
*
|
* Move the location of the iterator such that the next read will
|
* be the next location of the iterator.
|
*/
|
void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
unsigned long flags;
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
rb_advance_iter(iter);
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
|
|
/**
|
* ring_buffer_size - return the size of the ring buffer (in bytes)
|
* @buffer: The ring buffer.
|
* @cpu: The CPU to get ring buffer size from.
|
*/
|
unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
|
{
|
/*
|
* Earlier, this method returned
|
* BUF_PAGE_SIZE * buffer->nr_pages
|
* Since the nr_pages field is now removed, we have converted this to
|
* return the per cpu buffer value.
|
*/
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return 0;
|
|
return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_size);
|
|
static void
|
rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
rb_head_page_deactivate(cpu_buffer);
|
|
cpu_buffer->head_page
|
= list_entry(cpu_buffer->pages, struct buffer_page, list);
|
local_set(&cpu_buffer->head_page->write, 0);
|
local_set(&cpu_buffer->head_page->entries, 0);
|
local_set(&cpu_buffer->head_page->page->commit, 0);
|
|
cpu_buffer->head_page->read = 0;
|
|
cpu_buffer->tail_page = cpu_buffer->head_page;
|
cpu_buffer->commit_page = cpu_buffer->head_page;
|
|
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
local_set(&cpu_buffer->reader_page->write, 0);
|
local_set(&cpu_buffer->reader_page->entries, 0);
|
local_set(&cpu_buffer->reader_page->page->commit, 0);
|
cpu_buffer->reader_page->read = 0;
|
|
local_set(&cpu_buffer->entries_bytes, 0);
|
local_set(&cpu_buffer->overrun, 0);
|
local_set(&cpu_buffer->commit_overrun, 0);
|
local_set(&cpu_buffer->dropped_events, 0);
|
local_set(&cpu_buffer->entries, 0);
|
local_set(&cpu_buffer->committing, 0);
|
local_set(&cpu_buffer->commits, 0);
|
local_set(&cpu_buffer->pages_touched, 0);
|
local_set(&cpu_buffer->pages_lost, 0);
|
local_set(&cpu_buffer->pages_read, 0);
|
cpu_buffer->last_pages_touch = 0;
|
cpu_buffer->shortest_full = 0;
|
cpu_buffer->read = 0;
|
cpu_buffer->read_bytes = 0;
|
|
rb_time_set(&cpu_buffer->write_stamp, 0);
|
rb_time_set(&cpu_buffer->before_stamp, 0);
|
|
cpu_buffer->lost_events = 0;
|
cpu_buffer->last_overrun = 0;
|
|
rb_head_page_activate(cpu_buffer);
|
}
|
|
/* Must have disabled the cpu buffer then done a synchronize_rcu */
|
static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
|
{
|
unsigned long flags;
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
|
goto out;
|
|
arch_spin_lock(&cpu_buffer->lock);
|
|
rb_reset_cpu(cpu_buffer);
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
|
out:
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
}
|
|
/**
|
* ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
|
* @buffer: The ring buffer to reset a per cpu buffer of
|
* @cpu: The CPU buffer to be reset
|
*/
|
void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return;
|
|
/* prevent another thread from changing buffer sizes */
|
mutex_lock(&buffer->mutex);
|
|
atomic_inc(&cpu_buffer->resize_disabled);
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
/* Make sure all commits have finished */
|
synchronize_rcu();
|
|
reset_disabled_cpu_buffer(cpu_buffer);
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
atomic_dec(&cpu_buffer->resize_disabled);
|
|
mutex_unlock(&buffer->mutex);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
|
|
/**
|
* ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
|
* @buffer: The ring buffer to reset a per cpu buffer of
|
* @cpu: The CPU buffer to be reset
|
*/
|
void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
int cpu;
|
|
/* prevent another thread from changing buffer sizes */
|
mutex_lock(&buffer->mutex);
|
|
for_each_online_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
|
atomic_inc(&cpu_buffer->resize_disabled);
|
atomic_inc(&cpu_buffer->record_disabled);
|
}
|
|
/* Make sure all commits have finished */
|
synchronize_rcu();
|
|
for_each_online_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
|
reset_disabled_cpu_buffer(cpu_buffer);
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
atomic_dec(&cpu_buffer->resize_disabled);
|
}
|
|
mutex_unlock(&buffer->mutex);
|
}
|
|
/**
|
* ring_buffer_reset - reset a ring buffer
|
* @buffer: The ring buffer to reset all cpu buffers
|
*/
|
void ring_buffer_reset(struct trace_buffer *buffer)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
int cpu;
|
|
/* prevent another thread from changing buffer sizes */
|
mutex_lock(&buffer->mutex);
|
|
for_each_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
|
atomic_inc(&cpu_buffer->resize_disabled);
|
atomic_inc(&cpu_buffer->record_disabled);
|
}
|
|
/* Make sure all commits have finished */
|
synchronize_rcu();
|
|
for_each_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
|
reset_disabled_cpu_buffer(cpu_buffer);
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
atomic_dec(&cpu_buffer->resize_disabled);
|
}
|
|
mutex_unlock(&buffer->mutex);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_reset);
|
|
/**
|
* rind_buffer_empty - is the ring buffer empty?
|
* @buffer: The ring buffer to test
|
*/
|
bool ring_buffer_empty(struct trace_buffer *buffer)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
unsigned long flags;
|
bool dolock;
|
int cpu;
|
int ret;
|
|
/* yes this is racy, but if you don't like the race, lock the buffer */
|
for_each_buffer_cpu(buffer, cpu) {
|
cpu_buffer = buffer->buffers[cpu];
|
local_irq_save(flags);
|
dolock = rb_reader_lock(cpu_buffer);
|
ret = rb_per_cpu_empty(cpu_buffer);
|
rb_reader_unlock(cpu_buffer, dolock);
|
local_irq_restore(flags);
|
|
if (!ret)
|
return false;
|
}
|
|
return true;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_empty);
|
|
/**
|
* ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
|
* @buffer: The ring buffer
|
* @cpu: The CPU buffer to test
|
*/
|
bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
unsigned long flags;
|
bool dolock;
|
int ret;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return true;
|
|
cpu_buffer = buffer->buffers[cpu];
|
local_irq_save(flags);
|
dolock = rb_reader_lock(cpu_buffer);
|
ret = rb_per_cpu_empty(cpu_buffer);
|
rb_reader_unlock(cpu_buffer, dolock);
|
local_irq_restore(flags);
|
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
|
|
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
|
/**
|
* ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
|
* @buffer_a: One buffer to swap with
|
* @buffer_b: The other buffer to swap with
|
* @cpu: the CPU of the buffers to swap
|
*
|
* This function is useful for tracers that want to take a "snapshot"
|
* of a CPU buffer and has another back up buffer lying around.
|
* it is expected that the tracer handles the cpu buffer not being
|
* used at the moment.
|
*/
|
int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
|
struct trace_buffer *buffer_b, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer_a;
|
struct ring_buffer_per_cpu *cpu_buffer_b;
|
int ret = -EINVAL;
|
|
if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
|
!cpumask_test_cpu(cpu, buffer_b->cpumask))
|
goto out;
|
|
cpu_buffer_a = buffer_a->buffers[cpu];
|
cpu_buffer_b = buffer_b->buffers[cpu];
|
|
/* At least make sure the two buffers are somewhat the same */
|
if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
|
goto out;
|
|
ret = -EAGAIN;
|
|
if (atomic_read(&buffer_a->record_disabled))
|
goto out;
|
|
if (atomic_read(&buffer_b->record_disabled))
|
goto out;
|
|
if (atomic_read(&cpu_buffer_a->record_disabled))
|
goto out;
|
|
if (atomic_read(&cpu_buffer_b->record_disabled))
|
goto out;
|
|
/*
|
* We can't do a synchronize_rcu here because this
|
* function can be called in atomic context.
|
* Normally this will be called from the same CPU as cpu.
|
* If not it's up to the caller to protect this.
|
*/
|
atomic_inc(&cpu_buffer_a->record_disabled);
|
atomic_inc(&cpu_buffer_b->record_disabled);
|
|
ret = -EBUSY;
|
if (local_read(&cpu_buffer_a->committing))
|
goto out_dec;
|
if (local_read(&cpu_buffer_b->committing))
|
goto out_dec;
|
|
buffer_a->buffers[cpu] = cpu_buffer_b;
|
buffer_b->buffers[cpu] = cpu_buffer_a;
|
|
cpu_buffer_b->buffer = buffer_a;
|
cpu_buffer_a->buffer = buffer_b;
|
|
ret = 0;
|
|
out_dec:
|
atomic_dec(&cpu_buffer_a->record_disabled);
|
atomic_dec(&cpu_buffer_b->record_disabled);
|
out:
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
|
#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
|
|
/**
|
* ring_buffer_alloc_read_page - allocate a page to read from buffer
|
* @buffer: the buffer to allocate for.
|
* @cpu: the cpu buffer to allocate.
|
*
|
* This function is used in conjunction with ring_buffer_read_page.
|
* When reading a full page from the ring buffer, these functions
|
* can be used to speed up the process. The calling function should
|
* allocate a few pages first with this function. Then when it
|
* needs to get pages from the ring buffer, it passes the result
|
* of this function into ring_buffer_read_page, which will swap
|
* the page that was allocated, with the read page of the buffer.
|
*
|
* Returns:
|
* The page allocated, or ERR_PTR
|
*/
|
void *ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer;
|
struct buffer_data_page *bpage = NULL;
|
unsigned long flags;
|
struct page *page;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
return ERR_PTR(-ENODEV);
|
|
cpu_buffer = buffer->buffers[cpu];
|
local_irq_save(flags);
|
arch_spin_lock(&cpu_buffer->lock);
|
|
if (cpu_buffer->free_page) {
|
bpage = cpu_buffer->free_page;
|
cpu_buffer->free_page = NULL;
|
}
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
local_irq_restore(flags);
|
|
if (bpage)
|
goto out;
|
|
page = alloc_pages_node(cpu_to_node(cpu),
|
GFP_KERNEL | __GFP_NORETRY, 0);
|
if (!page)
|
return ERR_PTR(-ENOMEM);
|
|
bpage = page_address(page);
|
|
out:
|
rb_init_page(bpage);
|
|
return bpage;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
|
|
/**
|
* ring_buffer_free_read_page - free an allocated read page
|
* @buffer: the buffer the page was allocate for
|
* @cpu: the cpu buffer the page came from
|
* @data: the page to free
|
*
|
* Free a page allocated from ring_buffer_alloc_read_page.
|
*/
|
void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
struct buffer_data_page *bpage = data;
|
struct page *page = virt_to_page(bpage);
|
unsigned long flags;
|
|
/* If the page is still in use someplace else, we can't reuse it */
|
if (page_ref_count(page) > 1)
|
goto out;
|
|
local_irq_save(flags);
|
arch_spin_lock(&cpu_buffer->lock);
|
|
if (!cpu_buffer->free_page) {
|
cpu_buffer->free_page = bpage;
|
bpage = NULL;
|
}
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
local_irq_restore(flags);
|
|
out:
|
free_page((unsigned long)bpage);
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
|
|
/**
|
* ring_buffer_read_page - extract a page from the ring buffer
|
* @buffer: buffer to extract from
|
* @data_page: the page to use allocated from ring_buffer_alloc_read_page
|
* @len: amount to extract
|
* @cpu: the cpu of the buffer to extract
|
* @full: should the extraction only happen when the page is full.
|
*
|
* This function will pull out a page from the ring buffer and consume it.
|
* @data_page must be the address of the variable that was returned
|
* from ring_buffer_alloc_read_page. This is because the page might be used
|
* to swap with a page in the ring buffer.
|
*
|
* for example:
|
* rpage = ring_buffer_alloc_read_page(buffer, cpu);
|
* if (IS_ERR(rpage))
|
* return PTR_ERR(rpage);
|
* ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
|
* if (ret >= 0)
|
* process_page(rpage, ret);
|
*
|
* When @full is set, the function will not return true unless
|
* the writer is off the reader page.
|
*
|
* Note: it is up to the calling functions to handle sleeps and wakeups.
|
* The ring buffer can be used anywhere in the kernel and can not
|
* blindly call wake_up. The layer that uses the ring buffer must be
|
* responsible for that.
|
*
|
* Returns:
|
* >=0 if data has been transferred, returns the offset of consumed data.
|
* <0 if no data has been transferred.
|
*/
|
int ring_buffer_read_page(struct trace_buffer *buffer,
|
void **data_page, size_t len, int cpu, int full)
|
{
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
struct ring_buffer_event *event;
|
struct buffer_data_page *bpage;
|
struct buffer_page *reader;
|
unsigned long missed_events;
|
unsigned long flags;
|
unsigned int commit;
|
unsigned int read;
|
u64 save_timestamp;
|
int ret = -1;
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
goto out;
|
|
/*
|
* If len is not big enough to hold the page header, then
|
* we can not copy anything.
|
*/
|
if (len <= BUF_PAGE_HDR_SIZE)
|
goto out;
|
|
len -= BUF_PAGE_HDR_SIZE;
|
|
if (!data_page)
|
goto out;
|
|
bpage = *data_page;
|
if (!bpage)
|
goto out;
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
reader = rb_get_reader_page(cpu_buffer);
|
if (!reader)
|
goto out_unlock;
|
|
event = rb_reader_event(cpu_buffer);
|
|
read = reader->read;
|
commit = rb_page_commit(reader);
|
|
/* Check if any events were dropped */
|
missed_events = cpu_buffer->lost_events;
|
|
/*
|
* If this page has been partially read or
|
* if len is not big enough to read the rest of the page or
|
* a writer is still on the page, then
|
* we must copy the data from the page to the buffer.
|
* Otherwise, we can simply swap the page with the one passed in.
|
*/
|
if (read || (len < (commit - read)) ||
|
cpu_buffer->reader_page == cpu_buffer->commit_page) {
|
struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
|
unsigned int rpos = read;
|
unsigned int pos = 0;
|
unsigned int size;
|
|
/*
|
* If a full page is expected, this can still be returned
|
* if there's been a previous partial read and the
|
* rest of the page can be read and the commit page is off
|
* the reader page.
|
*/
|
if (full &&
|
(!read || (len < (commit - read)) ||
|
cpu_buffer->reader_page == cpu_buffer->commit_page))
|
goto out_unlock;
|
|
if (len > (commit - read))
|
len = (commit - read);
|
|
/* Always keep the time extend and data together */
|
size = rb_event_ts_length(event);
|
|
if (len < size)
|
goto out_unlock;
|
|
/* save the current timestamp, since the user will need it */
|
save_timestamp = cpu_buffer->read_stamp;
|
|
/* Need to copy one event at a time */
|
do {
|
/* We need the size of one event, because
|
* rb_advance_reader only advances by one event,
|
* whereas rb_event_ts_length may include the size of
|
* one or two events.
|
* We have already ensured there's enough space if this
|
* is a time extend. */
|
size = rb_event_length(event);
|
memcpy(bpage->data + pos, rpage->data + rpos, size);
|
|
len -= size;
|
|
rb_advance_reader(cpu_buffer);
|
rpos = reader->read;
|
pos += size;
|
|
if (rpos >= commit)
|
break;
|
|
event = rb_reader_event(cpu_buffer);
|
/* Always keep the time extend and data together */
|
size = rb_event_ts_length(event);
|
} while (len >= size);
|
|
/* update bpage */
|
local_set(&bpage->commit, pos);
|
bpage->time_stamp = save_timestamp;
|
|
/* we copied everything to the beginning */
|
read = 0;
|
} else {
|
/* update the entry counter */
|
cpu_buffer->read += rb_page_entries(reader);
|
cpu_buffer->read_bytes += BUF_PAGE_SIZE;
|
|
/* swap the pages */
|
rb_init_page(bpage);
|
bpage = reader->page;
|
reader->page = *data_page;
|
local_set(&reader->write, 0);
|
local_set(&reader->entries, 0);
|
reader->read = 0;
|
*data_page = bpage;
|
|
/*
|
* Use the real_end for the data size,
|
* This gives us a chance to store the lost events
|
* on the page.
|
*/
|
if (reader->real_end)
|
local_set(&bpage->commit, reader->real_end);
|
}
|
ret = read;
|
|
cpu_buffer->lost_events = 0;
|
|
commit = local_read(&bpage->commit);
|
/*
|
* Set a flag in the commit field if we lost events
|
*/
|
if (missed_events) {
|
/* If there is room at the end of the page to save the
|
* missed events, then record it there.
|
*/
|
if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
|
memcpy(&bpage->data[commit], &missed_events,
|
sizeof(missed_events));
|
local_add(RB_MISSED_STORED, &bpage->commit);
|
commit += sizeof(missed_events);
|
}
|
local_add(RB_MISSED_EVENTS, &bpage->commit);
|
}
|
|
/*
|
* This page may be off to user land. Zero it out here.
|
*/
|
if (commit < BUF_PAGE_SIZE)
|
memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
|
|
out_unlock:
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
out:
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(ring_buffer_read_page);
|
|
/*
|
* We only allocate new buffers, never free them if the CPU goes down.
|
* If we were to free the buffer, then the user would lose any trace that was in
|
* the buffer.
|
*/
|
int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
|
{
|
struct trace_buffer *buffer;
|
long nr_pages_same;
|
int cpu_i;
|
unsigned long nr_pages;
|
|
buffer = container_of(node, struct trace_buffer, node);
|
if (cpumask_test_cpu(cpu, buffer->cpumask))
|
return 0;
|
|
nr_pages = 0;
|
nr_pages_same = 1;
|
/* check if all cpu sizes are same */
|
for_each_buffer_cpu(buffer, cpu_i) {
|
/* fill in the size from first enabled cpu */
|
if (nr_pages == 0)
|
nr_pages = buffer->buffers[cpu_i]->nr_pages;
|
if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
|
nr_pages_same = 0;
|
break;
|
}
|
}
|
/* allocate minimum pages, user can later expand it */
|
if (!nr_pages_same)
|
nr_pages = 2;
|
buffer->buffers[cpu] =
|
rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
|
if (!buffer->buffers[cpu]) {
|
WARN(1, "failed to allocate ring buffer on CPU %u\n",
|
cpu);
|
return -ENOMEM;
|
}
|
smp_wmb();
|
cpumask_set_cpu(cpu, buffer->cpumask);
|
return 0;
|
}
|
|
#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
|
/*
|
* This is a basic integrity check of the ring buffer.
|
* Late in the boot cycle this test will run when configured in.
|
* It will kick off a thread per CPU that will go into a loop
|
* writing to the per cpu ring buffer various sizes of data.
|
* Some of the data will be large items, some small.
|
*
|
* Another thread is created that goes into a spin, sending out
|
* IPIs to the other CPUs to also write into the ring buffer.
|
* this is to test the nesting ability of the buffer.
|
*
|
* Basic stats are recorded and reported. If something in the
|
* ring buffer should happen that's not expected, a big warning
|
* is displayed and all ring buffers are disabled.
|
*/
|
static struct task_struct *rb_threads[NR_CPUS] __initdata;
|
|
struct rb_test_data {
|
struct trace_buffer *buffer;
|
unsigned long events;
|
unsigned long bytes_written;
|
unsigned long bytes_alloc;
|
unsigned long bytes_dropped;
|
unsigned long events_nested;
|
unsigned long bytes_written_nested;
|
unsigned long bytes_alloc_nested;
|
unsigned long bytes_dropped_nested;
|
int min_size_nested;
|
int max_size_nested;
|
int max_size;
|
int min_size;
|
int cpu;
|
int cnt;
|
};
|
|
static struct rb_test_data rb_data[NR_CPUS] __initdata;
|
|
/* 1 meg per cpu */
|
#define RB_TEST_BUFFER_SIZE 1048576
|
|
static char rb_string[] __initdata =
|
"abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
|
"?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
|
"!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
|
|
static bool rb_test_started __initdata;
|
|
struct rb_item {
|
int size;
|
char str[];
|
};
|
|
static __init int rb_write_something(struct rb_test_data *data, bool nested)
|
{
|
struct ring_buffer_event *event;
|
struct rb_item *item;
|
bool started;
|
int event_len;
|
int size;
|
int len;
|
int cnt;
|
|
/* Have nested writes different that what is written */
|
cnt = data->cnt + (nested ? 27 : 0);
|
|
/* Multiply cnt by ~e, to make some unique increment */
|
size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
|
|
len = size + sizeof(struct rb_item);
|
|
started = rb_test_started;
|
/* read rb_test_started before checking buffer enabled */
|
smp_rmb();
|
|
event = ring_buffer_lock_reserve(data->buffer, len);
|
if (!event) {
|
/* Ignore dropped events before test starts. */
|
if (started) {
|
if (nested)
|
data->bytes_dropped += len;
|
else
|
data->bytes_dropped_nested += len;
|
}
|
return len;
|
}
|
|
event_len = ring_buffer_event_length(event);
|
|
if (RB_WARN_ON(data->buffer, event_len < len))
|
goto out;
|
|
item = ring_buffer_event_data(event);
|
item->size = size;
|
memcpy(item->str, rb_string, size);
|
|
if (nested) {
|
data->bytes_alloc_nested += event_len;
|
data->bytes_written_nested += len;
|
data->events_nested++;
|
if (!data->min_size_nested || len < data->min_size_nested)
|
data->min_size_nested = len;
|
if (len > data->max_size_nested)
|
data->max_size_nested = len;
|
} else {
|
data->bytes_alloc += event_len;
|
data->bytes_written += len;
|
data->events++;
|
if (!data->min_size || len < data->min_size)
|
data->max_size = len;
|
if (len > data->max_size)
|
data->max_size = len;
|
}
|
|
out:
|
ring_buffer_unlock_commit(data->buffer, event);
|
|
return 0;
|
}
|
|
static __init int rb_test(void *arg)
|
{
|
struct rb_test_data *data = arg;
|
|
while (!kthread_should_stop()) {
|
rb_write_something(data, false);
|
data->cnt++;
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
/* Now sleep between a min of 100-300us and a max of 1ms */
|
usleep_range(((data->cnt % 3) + 1) * 100, 1000);
|
}
|
|
return 0;
|
}
|
|
static __init void rb_ipi(void *ignore)
|
{
|
struct rb_test_data *data;
|
int cpu = smp_processor_id();
|
|
data = &rb_data[cpu];
|
rb_write_something(data, true);
|
}
|
|
static __init int rb_hammer_test(void *arg)
|
{
|
while (!kthread_should_stop()) {
|
|
/* Send an IPI to all cpus to write data! */
|
smp_call_function(rb_ipi, NULL, 1);
|
/* No sleep, but for non preempt, let others run */
|
schedule();
|
}
|
|
return 0;
|
}
|
|
static __init int test_ringbuffer(void)
|
{
|
struct task_struct *rb_hammer;
|
struct trace_buffer *buffer;
|
int cpu;
|
int ret = 0;
|
|
if (security_locked_down(LOCKDOWN_TRACEFS)) {
|
pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
|
return 0;
|
}
|
|
pr_info("Running ring buffer tests...\n");
|
|
buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
|
if (WARN_ON(!buffer))
|
return 0;
|
|
/* Disable buffer so that threads can't write to it yet */
|
ring_buffer_record_off(buffer);
|
|
for_each_online_cpu(cpu) {
|
rb_data[cpu].buffer = buffer;
|
rb_data[cpu].cpu = cpu;
|
rb_data[cpu].cnt = cpu;
|
rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
|
"rbtester/%d", cpu);
|
if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
|
pr_cont("FAILED\n");
|
ret = PTR_ERR(rb_threads[cpu]);
|
goto out_free;
|
}
|
|
kthread_bind(rb_threads[cpu], cpu);
|
wake_up_process(rb_threads[cpu]);
|
}
|
|
/* Now create the rb hammer! */
|
rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
|
if (WARN_ON(IS_ERR(rb_hammer))) {
|
pr_cont("FAILED\n");
|
ret = PTR_ERR(rb_hammer);
|
goto out_free;
|
}
|
|
ring_buffer_record_on(buffer);
|
/*
|
* Show buffer is enabled before setting rb_test_started.
|
* Yes there's a small race window where events could be
|
* dropped and the thread wont catch it. But when a ring
|
* buffer gets enabled, there will always be some kind of
|
* delay before other CPUs see it. Thus, we don't care about
|
* those dropped events. We care about events dropped after
|
* the threads see that the buffer is active.
|
*/
|
smp_wmb();
|
rb_test_started = true;
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
/* Just run for 10 seconds */;
|
schedule_timeout(10 * HZ);
|
|
kthread_stop(rb_hammer);
|
|
out_free:
|
for_each_online_cpu(cpu) {
|
if (!rb_threads[cpu])
|
break;
|
kthread_stop(rb_threads[cpu]);
|
}
|
if (ret) {
|
ring_buffer_free(buffer);
|
return ret;
|
}
|
|
/* Report! */
|
pr_info("finished\n");
|
for_each_online_cpu(cpu) {
|
struct ring_buffer_event *event;
|
struct rb_test_data *data = &rb_data[cpu];
|
struct rb_item *item;
|
unsigned long total_events;
|
unsigned long total_dropped;
|
unsigned long total_written;
|
unsigned long total_alloc;
|
unsigned long total_read = 0;
|
unsigned long total_size = 0;
|
unsigned long total_len = 0;
|
unsigned long total_lost = 0;
|
unsigned long lost;
|
int big_event_size;
|
int small_event_size;
|
|
ret = -1;
|
|
total_events = data->events + data->events_nested;
|
total_written = data->bytes_written + data->bytes_written_nested;
|
total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
|
total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
|
|
big_event_size = data->max_size + data->max_size_nested;
|
small_event_size = data->min_size + data->min_size_nested;
|
|
pr_info("CPU %d:\n", cpu);
|
pr_info(" events: %ld\n", total_events);
|
pr_info(" dropped bytes: %ld\n", total_dropped);
|
pr_info(" alloced bytes: %ld\n", total_alloc);
|
pr_info(" written bytes: %ld\n", total_written);
|
pr_info(" biggest event: %d\n", big_event_size);
|
pr_info(" smallest event: %d\n", small_event_size);
|
|
if (RB_WARN_ON(buffer, total_dropped))
|
break;
|
|
ret = 0;
|
|
while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
|
total_lost += lost;
|
item = ring_buffer_event_data(event);
|
total_len += ring_buffer_event_length(event);
|
total_size += item->size + sizeof(struct rb_item);
|
if (memcmp(&item->str[0], rb_string, item->size) != 0) {
|
pr_info("FAILED!\n");
|
pr_info("buffer had: %.*s\n", item->size, item->str);
|
pr_info("expected: %.*s\n", item->size, rb_string);
|
RB_WARN_ON(buffer, 1);
|
ret = -1;
|
break;
|
}
|
total_read++;
|
}
|
if (ret)
|
break;
|
|
ret = -1;
|
|
pr_info(" read events: %ld\n", total_read);
|
pr_info(" lost events: %ld\n", total_lost);
|
pr_info(" total events: %ld\n", total_lost + total_read);
|
pr_info(" recorded len bytes: %ld\n", total_len);
|
pr_info(" recorded size bytes: %ld\n", total_size);
|
if (total_lost)
|
pr_info(" With dropped events, record len and size may not match\n"
|
" alloced and written from above\n");
|
if (!total_lost) {
|
if (RB_WARN_ON(buffer, total_len != total_alloc ||
|
total_size != total_written))
|
break;
|
}
|
if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
|
break;
|
|
ret = 0;
|
}
|
if (!ret)
|
pr_info("Ring buffer PASSED!\n");
|
|
ring_buffer_free(buffer);
|
return 0;
|
}
|
|
late_initcall(test_ringbuffer);
|
#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
|
