From 102a0743326a03cd1a1202ceda21e175b7d3575c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Tue, 20 Feb 2024 01:20:52 +0000
Subject: [PATCH] add new system file
---
kernel/kernel/rcu/srcutiny.c | 210 ++++++++++++++++++++++++++++++++++------------------
1 files changed, 138 insertions(+), 72 deletions(-)
diff --git a/kernel/kernel/rcu/srcutiny.c b/kernel/kernel/rcu/srcutiny.c
index 04fc2ed..26344dc 100644
--- a/kernel/kernel/rcu/srcutiny.c
+++ b/kernel/kernel/rcu/srcutiny.c
@@ -1,24 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0+
/*
* Sleepable Read-Copy Update mechanism for mutual exclusion,
* tiny version for non-preemptible single-CPU use.
*
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, you can access it online at
- * http://www.gnu.org/licenses/gpl-2.0.html.
- *
* Copyright (C) IBM Corporation, 2017
*
- * Author: Paul McKenney <paulmck@us.ibm.com>
+ * Author: Paul McKenney <paulmck@linux.ibm.com>
*/
#include <linux/export.h>
@@ -34,30 +21,34 @@
#include "rcu.h"
int rcu_scheduler_active __read_mostly;
+static LIST_HEAD(srcu_boot_list);
+static bool srcu_init_done;
-static int init_srcu_struct_fields(struct srcu_struct *sp)
+static int init_srcu_struct_fields(struct srcu_struct *ssp)
{
- sp->srcu_lock_nesting[0] = 0;
- sp->srcu_lock_nesting[1] = 0;
- init_swait_queue_head(&sp->srcu_wq);
- sp->srcu_cb_head = NULL;
- sp->srcu_cb_tail = &sp->srcu_cb_head;
- sp->srcu_gp_running = false;
- sp->srcu_gp_waiting = false;
- sp->srcu_idx = 0;
- INIT_WORK(&sp->srcu_work, srcu_drive_gp);
+ ssp->srcu_lock_nesting[0] = 0;
+ ssp->srcu_lock_nesting[1] = 0;
+ init_swait_queue_head(&ssp->srcu_wq);
+ ssp->srcu_cb_head = NULL;
+ ssp->srcu_cb_tail = &ssp->srcu_cb_head;
+ ssp->srcu_gp_running = false;
+ ssp->srcu_gp_waiting = false;
+ ssp->srcu_idx = 0;
+ ssp->srcu_idx_max = 0;
+ INIT_WORK(&ssp->srcu_work, srcu_drive_gp);
+ INIT_LIST_HEAD(&ssp->srcu_work.entry);
return 0;
}
#ifdef CONFIG_DEBUG_LOCK_ALLOC
-int __init_srcu_struct(struct srcu_struct *sp, const char *name,
+int __init_srcu_struct(struct srcu_struct *ssp, const char *name,
struct lock_class_key *key)
{
/* Don't re-initialize a lock while it is held. */
- debug_check_no_locks_freed((void *)sp, sizeof(*sp));
- lockdep_init_map(&sp->dep_map, name, key, 0);
- return init_srcu_struct_fields(sp);
+ debug_check_no_locks_freed((void *)ssp, sizeof(*ssp));
+ lockdep_init_map(&ssp->dep_map, name, key, 0);
+ return init_srcu_struct_fields(ssp);
}
EXPORT_SYMBOL_GPL(__init_srcu_struct);
@@ -65,15 +56,15 @@
/*
* init_srcu_struct - initialize a sleep-RCU structure
- * @sp: structure to initialize.
+ * @ssp: structure to initialize.
*
* Must invoke this on a given srcu_struct before passing that srcu_struct
* to any other function. Each srcu_struct represents a separate domain
* of SRCU protection.
*/
-int init_srcu_struct(struct srcu_struct *sp)
+int init_srcu_struct(struct srcu_struct *ssp)
{
- return init_srcu_struct_fields(sp);
+ return init_srcu_struct_fields(ssp);
}
EXPORT_SYMBOL_GPL(init_srcu_struct);
@@ -81,42 +72,41 @@
/*
* cleanup_srcu_struct - deconstruct a sleep-RCU structure
- * @sp: structure to clean up.
+ * @ssp: structure to clean up.
*
* Must invoke this after you are finished using a given srcu_struct that
* was initialized via init_srcu_struct(), else you leak memory.
*/
-void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced)
+void cleanup_srcu_struct(struct srcu_struct *ssp)
{
- WARN_ON(sp->srcu_lock_nesting[0] || sp->srcu_lock_nesting[1]);
- if (quiesced)
- WARN_ON(work_pending(&sp->srcu_work));
- else
- flush_work(&sp->srcu_work);
- WARN_ON(sp->srcu_gp_running);
- WARN_ON(sp->srcu_gp_waiting);
- WARN_ON(sp->srcu_cb_head);
- WARN_ON(&sp->srcu_cb_head != sp->srcu_cb_tail);
+ WARN_ON(ssp->srcu_lock_nesting[0] || ssp->srcu_lock_nesting[1]);
+ flush_work(&ssp->srcu_work);
+ WARN_ON(ssp->srcu_gp_running);
+ WARN_ON(ssp->srcu_gp_waiting);
+ WARN_ON(ssp->srcu_cb_head);
+ WARN_ON(&ssp->srcu_cb_head != ssp->srcu_cb_tail);
+ WARN_ON(ssp->srcu_idx != ssp->srcu_idx_max);
+ WARN_ON(ssp->srcu_idx & 0x1);
}
-EXPORT_SYMBOL_GPL(_cleanup_srcu_struct);
+EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
/*
* Removes the count for the old reader from the appropriate element of
* the srcu_struct.
*/
-void __srcu_read_unlock(struct srcu_struct *sp, int idx)
+void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
{
- int newval = sp->srcu_lock_nesting[idx] - 1;
+ int newval = ssp->srcu_lock_nesting[idx] - 1;
- WRITE_ONCE(sp->srcu_lock_nesting[idx], newval);
- if (!newval && READ_ONCE(sp->srcu_gp_waiting))
- swake_up_one(&sp->srcu_wq);
+ WRITE_ONCE(ssp->srcu_lock_nesting[idx], newval);
+ if (!newval && READ_ONCE(ssp->srcu_gp_waiting))
+ swake_up_one(&ssp->srcu_wq);
}
EXPORT_SYMBOL_GPL(__srcu_read_unlock);
/*
* Workqueue handler to drive one grace period and invoke any callbacks
- * that become ready as a result. Single-CPU and !PREEMPT operation
+ * that become ready as a result. Single-CPU and !PREEMPTION operation
* means that we get away with murder on synchronization. ;-)
*/
void srcu_drive_gp(struct work_struct *wp)
@@ -124,24 +114,25 @@
int idx;
struct rcu_head *lh;
struct rcu_head *rhp;
- struct srcu_struct *sp;
+ struct srcu_struct *ssp;
- sp = container_of(wp, struct srcu_struct, srcu_work);
- if (sp->srcu_gp_running || !READ_ONCE(sp->srcu_cb_head))
+ ssp = container_of(wp, struct srcu_struct, srcu_work);
+ if (ssp->srcu_gp_running || USHORT_CMP_GE(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max)))
return; /* Already running or nothing to do. */
/* Remove recently arrived callbacks and wait for readers. */
- WRITE_ONCE(sp->srcu_gp_running, true);
+ WRITE_ONCE(ssp->srcu_gp_running, true);
local_irq_disable();
- lh = sp->srcu_cb_head;
- sp->srcu_cb_head = NULL;
- sp->srcu_cb_tail = &sp->srcu_cb_head;
+ lh = ssp->srcu_cb_head;
+ ssp->srcu_cb_head = NULL;
+ ssp->srcu_cb_tail = &ssp->srcu_cb_head;
local_irq_enable();
- idx = sp->srcu_idx;
- WRITE_ONCE(sp->srcu_idx, !sp->srcu_idx);
- WRITE_ONCE(sp->srcu_gp_waiting, true); /* srcu_read_unlock() wakes! */
- swait_event_exclusive(sp->srcu_wq, !READ_ONCE(sp->srcu_lock_nesting[idx]));
- WRITE_ONCE(sp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */
+ idx = (ssp->srcu_idx & 0x2) / 2;
+ WRITE_ONCE(ssp->srcu_idx, ssp->srcu_idx + 1);
+ WRITE_ONCE(ssp->srcu_gp_waiting, true); /* srcu_read_unlock() wakes! */
+ swait_event_exclusive(ssp->srcu_wq, !READ_ONCE(ssp->srcu_lock_nesting[idx]));
+ WRITE_ONCE(ssp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */
+ WRITE_ONCE(ssp->srcu_idx, ssp->srcu_idx + 1);
/* Invoke the callbacks we removed above. */
while (lh) {
@@ -158,17 +149,33 @@
* at interrupt level, but the ->srcu_gp_running checks will
* straighten that out.
*/
- WRITE_ONCE(sp->srcu_gp_running, false);
- if (READ_ONCE(sp->srcu_cb_head))
- schedule_work(&sp->srcu_work);
+ WRITE_ONCE(ssp->srcu_gp_running, false);
+ if (USHORT_CMP_LT(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max)))
+ schedule_work(&ssp->srcu_work);
}
EXPORT_SYMBOL_GPL(srcu_drive_gp);
+
+static void srcu_gp_start_if_needed(struct srcu_struct *ssp)
+{
+ unsigned short cookie;
+
+ cookie = get_state_synchronize_srcu(ssp);
+ if (USHORT_CMP_GE(READ_ONCE(ssp->srcu_idx_max), cookie))
+ return;
+ WRITE_ONCE(ssp->srcu_idx_max, cookie);
+ if (!READ_ONCE(ssp->srcu_gp_running)) {
+ if (likely(srcu_init_done))
+ schedule_work(&ssp->srcu_work);
+ else if (list_empty(&ssp->srcu_work.entry))
+ list_add(&ssp->srcu_work.entry, &srcu_boot_list);
+ }
+}
/*
* Enqueue an SRCU callback on the specified srcu_struct structure,
* initiating grace-period processing if it is not already running.
*/
-void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp,
+void call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
rcu_callback_t func)
{
unsigned long flags;
@@ -176,31 +183,90 @@
rhp->func = func;
rhp->next = NULL;
local_irq_save(flags);
- *sp->srcu_cb_tail = rhp;
- sp->srcu_cb_tail = &rhp->next;
+ *ssp->srcu_cb_tail = rhp;
+ ssp->srcu_cb_tail = &rhp->next;
local_irq_restore(flags);
- if (!READ_ONCE(sp->srcu_gp_running))
- schedule_work(&sp->srcu_work);
+ srcu_gp_start_if_needed(ssp);
}
EXPORT_SYMBOL_GPL(call_srcu);
/*
* synchronize_srcu - wait for prior SRCU read-side critical-section completion
*/
-void synchronize_srcu(struct srcu_struct *sp)
+void synchronize_srcu(struct srcu_struct *ssp)
{
struct rcu_synchronize rs;
init_rcu_head_on_stack(&rs.head);
init_completion(&rs.completion);
- call_srcu(sp, &rs.head, wakeme_after_rcu);
+ call_srcu(ssp, &rs.head, wakeme_after_rcu);
wait_for_completion(&rs.completion);
destroy_rcu_head_on_stack(&rs.head);
}
EXPORT_SYMBOL_GPL(synchronize_srcu);
+/*
+ * get_state_synchronize_srcu - Provide an end-of-grace-period cookie
+ */
+unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp)
+{
+ unsigned long ret;
+
+ barrier();
+ ret = (READ_ONCE(ssp->srcu_idx) + 3) & ~0x1;
+ barrier();
+ return ret & USHRT_MAX;
+}
+EXPORT_SYMBOL_GPL(get_state_synchronize_srcu);
+
+/*
+ * start_poll_synchronize_srcu - Provide cookie and start grace period
+ *
+ * The difference between this and get_state_synchronize_srcu() is that
+ * this function ensures that the poll_state_synchronize_srcu() will
+ * eventually return the value true.
+ */
+unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp)
+{
+ unsigned long ret = get_state_synchronize_srcu(ssp);
+
+ srcu_gp_start_if_needed(ssp);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(start_poll_synchronize_srcu);
+
+/*
+ * poll_state_synchronize_srcu - Has cookie's grace period ended?
+ */
+bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie)
+{
+ bool ret = USHORT_CMP_GE(READ_ONCE(ssp->srcu_idx), cookie);
+
+ barrier();
+ return ret;
+}
+EXPORT_SYMBOL_GPL(poll_state_synchronize_srcu);
+
/* Lockdep diagnostics. */
void __init rcu_scheduler_starting(void)
{
rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
}
+
+/*
+ * Queue work for srcu_struct structures with early boot callbacks.
+ * The work won't actually execute until the workqueue initialization
+ * phase that takes place after the scheduler starts.
+ */
+void __init srcu_init(void)
+{
+ struct srcu_struct *ssp;
+
+ srcu_init_done = true;
+ while (!list_empty(&srcu_boot_list)) {
+ ssp = list_first_entry(&srcu_boot_list,
+ struct srcu_struct, srcu_work.entry);
+ list_del_init(&ssp->srcu_work.entry);
+ schedule_work(&ssp->srcu_work);
+ }
+}
--
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