// SPDX-License-Identifier: GPL-2.0
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/*
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* Performance events callchain code, extracted from core.c:
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*
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* Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
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* Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
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* Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra
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* Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
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*/
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#include <linux/perf_event.h>
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#include <linux/slab.h>
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#include <linux/sched/task_stack.h>
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#include "internal.h"
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struct callchain_cpus_entries {
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struct rcu_head rcu_head;
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struct perf_callchain_entry *cpu_entries[];
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};
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int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH;
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int sysctl_perf_event_max_contexts_per_stack __read_mostly = PERF_MAX_CONTEXTS_PER_STACK;
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static inline size_t perf_callchain_entry__sizeof(void)
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{
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return (sizeof(struct perf_callchain_entry) +
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sizeof(__u64) * (sysctl_perf_event_max_stack +
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sysctl_perf_event_max_contexts_per_stack));
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}
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static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
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static atomic_t nr_callchain_events;
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static DEFINE_MUTEX(callchain_mutex);
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static struct callchain_cpus_entries *callchain_cpus_entries;
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__weak void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
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struct pt_regs *regs)
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{
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}
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__weak void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
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struct pt_regs *regs)
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{
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}
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static void release_callchain_buffers_rcu(struct rcu_head *head)
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{
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struct callchain_cpus_entries *entries;
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int cpu;
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entries = container_of(head, struct callchain_cpus_entries, rcu_head);
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for_each_possible_cpu(cpu)
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kfree(entries->cpu_entries[cpu]);
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kfree(entries);
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}
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static void release_callchain_buffers(void)
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{
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struct callchain_cpus_entries *entries;
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entries = callchain_cpus_entries;
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RCU_INIT_POINTER(callchain_cpus_entries, NULL);
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call_rcu(&entries->rcu_head, release_callchain_buffers_rcu);
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}
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static int alloc_callchain_buffers(void)
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{
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int cpu;
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int size;
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struct callchain_cpus_entries *entries;
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/*
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* We can't use the percpu allocation API for data that can be
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* accessed from NMI. Use a temporary manual per cpu allocation
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* until that gets sorted out.
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*/
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size = offsetof(struct callchain_cpus_entries, cpu_entries[nr_cpu_ids]);
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entries = kzalloc(size, GFP_KERNEL);
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if (!entries)
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return -ENOMEM;
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size = perf_callchain_entry__sizeof() * PERF_NR_CONTEXTS;
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for_each_possible_cpu(cpu) {
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entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL,
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cpu_to_node(cpu));
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if (!entries->cpu_entries[cpu])
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goto fail;
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}
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rcu_assign_pointer(callchain_cpus_entries, entries);
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return 0;
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fail:
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for_each_possible_cpu(cpu)
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kfree(entries->cpu_entries[cpu]);
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kfree(entries);
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return -ENOMEM;
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}
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int get_callchain_buffers(int event_max_stack)
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{
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int err = 0;
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int count;
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mutex_lock(&callchain_mutex);
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count = atomic_inc_return(&nr_callchain_events);
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if (WARN_ON_ONCE(count < 1)) {
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err = -EINVAL;
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goto exit;
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}
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/*
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* If requesting per event more than the global cap,
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* return a different error to help userspace figure
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* this out.
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*
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* And also do it here so that we have &callchain_mutex held.
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*/
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if (event_max_stack > sysctl_perf_event_max_stack) {
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err = -EOVERFLOW;
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goto exit;
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}
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if (count == 1)
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err = alloc_callchain_buffers();
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exit:
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if (err)
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atomic_dec(&nr_callchain_events);
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mutex_unlock(&callchain_mutex);
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return err;
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}
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void put_callchain_buffers(void)
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{
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if (atomic_dec_and_mutex_lock(&nr_callchain_events, &callchain_mutex)) {
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release_callchain_buffers();
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mutex_unlock(&callchain_mutex);
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}
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}
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struct perf_callchain_entry *get_callchain_entry(int *rctx)
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{
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int cpu;
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struct callchain_cpus_entries *entries;
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*rctx = get_recursion_context(this_cpu_ptr(callchain_recursion));
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if (*rctx == -1)
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return NULL;
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entries = rcu_dereference(callchain_cpus_entries);
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if (!entries) {
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put_recursion_context(this_cpu_ptr(callchain_recursion), *rctx);
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return NULL;
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}
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cpu = smp_processor_id();
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return (((void *)entries->cpu_entries[cpu]) +
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(*rctx * perf_callchain_entry__sizeof()));
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}
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void
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put_callchain_entry(int rctx)
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{
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put_recursion_context(this_cpu_ptr(callchain_recursion), rctx);
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}
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struct perf_callchain_entry *
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get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
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u32 max_stack, bool crosstask, bool add_mark)
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{
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struct perf_callchain_entry *entry;
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struct perf_callchain_entry_ctx ctx;
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int rctx;
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entry = get_callchain_entry(&rctx);
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if (!entry)
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return NULL;
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ctx.entry = entry;
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ctx.max_stack = max_stack;
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ctx.nr = entry->nr = init_nr;
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ctx.contexts = 0;
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ctx.contexts_maxed = false;
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if (kernel && !user_mode(regs)) {
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if (add_mark)
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perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL);
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perf_callchain_kernel(&ctx, regs);
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}
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if (user) {
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if (!user_mode(regs)) {
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if (current->mm)
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regs = task_pt_regs(current);
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else
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regs = NULL;
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}
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if (regs) {
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mm_segment_t fs;
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if (crosstask)
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goto exit_put;
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if (add_mark)
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perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);
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fs = force_uaccess_begin();
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perf_callchain_user(&ctx, regs);
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force_uaccess_end(fs);
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}
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}
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exit_put:
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put_callchain_entry(rctx);
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return entry;
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}
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/*
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* Used for sysctl_perf_event_max_stack and
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* sysctl_perf_event_max_contexts_per_stack.
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*/
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int perf_event_max_stack_handler(struct ctl_table *table, int write,
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void *buffer, size_t *lenp, loff_t *ppos)
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{
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int *value = table->data;
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int new_value = *value, ret;
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struct ctl_table new_table = *table;
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new_table.data = &new_value;
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ret = proc_dointvec_minmax(&new_table, write, buffer, lenp, ppos);
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if (ret || !write)
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return ret;
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mutex_lock(&callchain_mutex);
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if (atomic_read(&nr_callchain_events))
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ret = -EBUSY;
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else
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*value = new_value;
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mutex_unlock(&callchain_mutex);
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return ret;
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}
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