mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-21 08:19:28 +00:00
![Paul E. McKenney](/assets/img/avatar_default.png)
If the RCU callback-processing kthread has nothing to do, it parks in a wait_event(). If RCU remains idle for more than two minutes, the kernel complains about this. This commit changes from wait_event() to wait_event_interruptible() to prevent the kernel from complaining just because RCU is idle. Reported-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Thomas Weber <weber@corscience.de> Tested-by: Russell King <rmk+kernel@arm.linux.org.uk>
324 lines
8.4 KiB
C
324 lines
8.4 KiB
C
/*
|
|
* Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
|
|
*
|
|
* 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, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
|
|
*
|
|
* Copyright IBM Corporation, 2008
|
|
*
|
|
* Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
|
|
*
|
|
* For detailed explanation of Read-Copy Update mechanism see -
|
|
* Documentation/RCU
|
|
*/
|
|
#include <linux/moduleparam.h>
|
|
#include <linux/completion.h>
|
|
#include <linux/interrupt.h>
|
|
#include <linux/notifier.h>
|
|
#include <linux/rcupdate.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/module.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/types.h>
|
|
#include <linux/init.h>
|
|
#include <linux/time.h>
|
|
#include <linux/cpu.h>
|
|
|
|
/* Controls for rcu_kthread() kthread, replacing RCU_SOFTIRQ used previously. */
|
|
static struct task_struct *rcu_kthread_task;
|
|
static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq);
|
|
static unsigned long have_rcu_kthread_work;
|
|
static void invoke_rcu_kthread(void);
|
|
|
|
/* Forward declarations for rcutiny_plugin.h. */
|
|
struct rcu_ctrlblk;
|
|
static void rcu_process_callbacks(struct rcu_ctrlblk *rcp);
|
|
static int rcu_kthread(void *arg);
|
|
static void __call_rcu(struct rcu_head *head,
|
|
void (*func)(struct rcu_head *rcu),
|
|
struct rcu_ctrlblk *rcp);
|
|
|
|
#include "rcutiny_plugin.h"
|
|
|
|
#ifdef CONFIG_NO_HZ
|
|
|
|
static long rcu_dynticks_nesting = 1;
|
|
|
|
/*
|
|
* Enter dynticks-idle mode, which is an extended quiescent state
|
|
* if we have fully entered that mode (i.e., if the new value of
|
|
* dynticks_nesting is zero).
|
|
*/
|
|
void rcu_enter_nohz(void)
|
|
{
|
|
if (--rcu_dynticks_nesting == 0)
|
|
rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
|
|
}
|
|
|
|
/*
|
|
* Exit dynticks-idle mode, so that we are no longer in an extended
|
|
* quiescent state.
|
|
*/
|
|
void rcu_exit_nohz(void)
|
|
{
|
|
rcu_dynticks_nesting++;
|
|
}
|
|
|
|
#endif /* #ifdef CONFIG_NO_HZ */
|
|
|
|
/*
|
|
* Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc().
|
|
* Also disable irqs to avoid confusion due to interrupt handlers
|
|
* invoking call_rcu().
|
|
*/
|
|
static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
|
|
{
|
|
unsigned long flags;
|
|
|
|
local_irq_save(flags);
|
|
if (rcp->rcucblist != NULL &&
|
|
rcp->donetail != rcp->curtail) {
|
|
rcp->donetail = rcp->curtail;
|
|
local_irq_restore(flags);
|
|
return 1;
|
|
}
|
|
local_irq_restore(flags);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Record an rcu quiescent state. And an rcu_bh quiescent state while we
|
|
* are at it, given that any rcu quiescent state is also an rcu_bh
|
|
* quiescent state. Use "+" instead of "||" to defeat short circuiting.
|
|
*/
|
|
void rcu_sched_qs(int cpu)
|
|
{
|
|
if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
|
|
rcu_qsctr_help(&rcu_bh_ctrlblk))
|
|
invoke_rcu_kthread();
|
|
}
|
|
|
|
/*
|
|
* Record an rcu_bh quiescent state.
|
|
*/
|
|
void rcu_bh_qs(int cpu)
|
|
{
|
|
if (rcu_qsctr_help(&rcu_bh_ctrlblk))
|
|
invoke_rcu_kthread();
|
|
}
|
|
|
|
/*
|
|
* Check to see if the scheduling-clock interrupt came from an extended
|
|
* quiescent state, and, if so, tell RCU about it.
|
|
*/
|
|
void rcu_check_callbacks(int cpu, int user)
|
|
{
|
|
if (user ||
|
|
(idle_cpu(cpu) &&
|
|
!in_softirq() &&
|
|
hardirq_count() <= (1 << HARDIRQ_SHIFT)))
|
|
rcu_sched_qs(cpu);
|
|
else if (!in_softirq())
|
|
rcu_bh_qs(cpu);
|
|
rcu_preempt_check_callbacks();
|
|
}
|
|
|
|
/*
|
|
* Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
|
|
* whose grace period has elapsed.
|
|
*/
|
|
static void rcu_process_callbacks(struct rcu_ctrlblk *rcp)
|
|
{
|
|
struct rcu_head *next, *list;
|
|
unsigned long flags;
|
|
RCU_TRACE(int cb_count = 0);
|
|
|
|
/* If no RCU callbacks ready to invoke, just return. */
|
|
if (&rcp->rcucblist == rcp->donetail)
|
|
return;
|
|
|
|
/* Move the ready-to-invoke callbacks to a local list. */
|
|
local_irq_save(flags);
|
|
list = rcp->rcucblist;
|
|
rcp->rcucblist = *rcp->donetail;
|
|
*rcp->donetail = NULL;
|
|
if (rcp->curtail == rcp->donetail)
|
|
rcp->curtail = &rcp->rcucblist;
|
|
rcu_preempt_remove_callbacks(rcp);
|
|
rcp->donetail = &rcp->rcucblist;
|
|
local_irq_restore(flags);
|
|
|
|
/* Invoke the callbacks on the local list. */
|
|
while (list) {
|
|
next = list->next;
|
|
prefetch(next);
|
|
debug_rcu_head_unqueue(list);
|
|
local_bh_disable();
|
|
list->func(list);
|
|
local_bh_enable();
|
|
list = next;
|
|
RCU_TRACE(cb_count++);
|
|
}
|
|
RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
|
|
}
|
|
|
|
/*
|
|
* This kthread invokes RCU callbacks whose grace periods have
|
|
* elapsed. It is awakened as needed, and takes the place of the
|
|
* RCU_SOFTIRQ that was used previously for this purpose.
|
|
* This is a kthread, but it is never stopped, at least not until
|
|
* the system goes down.
|
|
*/
|
|
static int rcu_kthread(void *arg)
|
|
{
|
|
unsigned long work;
|
|
unsigned long morework;
|
|
unsigned long flags;
|
|
|
|
for (;;) {
|
|
wait_event_interruptible(rcu_kthread_wq,
|
|
have_rcu_kthread_work != 0);
|
|
morework = rcu_boost();
|
|
local_irq_save(flags);
|
|
work = have_rcu_kthread_work;
|
|
have_rcu_kthread_work = morework;
|
|
local_irq_restore(flags);
|
|
if (work) {
|
|
rcu_process_callbacks(&rcu_sched_ctrlblk);
|
|
rcu_process_callbacks(&rcu_bh_ctrlblk);
|
|
rcu_preempt_process_callbacks();
|
|
}
|
|
schedule_timeout_interruptible(1); /* Leave CPU for others. */
|
|
}
|
|
|
|
return 0; /* Not reached, but needed to shut gcc up. */
|
|
}
|
|
|
|
/*
|
|
* Wake up rcu_kthread() to process callbacks now eligible for invocation
|
|
* or to boost readers.
|
|
*/
|
|
static void invoke_rcu_kthread(void)
|
|
{
|
|
unsigned long flags;
|
|
|
|
local_irq_save(flags);
|
|
have_rcu_kthread_work = 1;
|
|
wake_up(&rcu_kthread_wq);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/*
|
|
* Wait for a grace period to elapse. But it is illegal to invoke
|
|
* synchronize_sched() from within an RCU read-side critical section.
|
|
* Therefore, any legal call to synchronize_sched() is a quiescent
|
|
* state, and so on a UP system, synchronize_sched() need do nothing.
|
|
* Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the
|
|
* benefits of doing might_sleep() to reduce latency.)
|
|
*
|
|
* Cool, huh? (Due to Josh Triplett.)
|
|
*
|
|
* But we want to make this a static inline later. The cond_resched()
|
|
* currently makes this problematic.
|
|
*/
|
|
void synchronize_sched(void)
|
|
{
|
|
cond_resched();
|
|
}
|
|
EXPORT_SYMBOL_GPL(synchronize_sched);
|
|
|
|
/*
|
|
* Helper function for call_rcu() and call_rcu_bh().
|
|
*/
|
|
static void __call_rcu(struct rcu_head *head,
|
|
void (*func)(struct rcu_head *rcu),
|
|
struct rcu_ctrlblk *rcp)
|
|
{
|
|
unsigned long flags;
|
|
|
|
debug_rcu_head_queue(head);
|
|
head->func = func;
|
|
head->next = NULL;
|
|
|
|
local_irq_save(flags);
|
|
*rcp->curtail = head;
|
|
rcp->curtail = &head->next;
|
|
RCU_TRACE(rcp->qlen++);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/*
|
|
* Post an RCU callback to be invoked after the end of an RCU-sched grace
|
|
* period. But since we have but one CPU, that would be after any
|
|
* quiescent state.
|
|
*/
|
|
void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
|
|
{
|
|
__call_rcu(head, func, &rcu_sched_ctrlblk);
|
|
}
|
|
EXPORT_SYMBOL_GPL(call_rcu_sched);
|
|
|
|
/*
|
|
* Post an RCU bottom-half callback to be invoked after any subsequent
|
|
* quiescent state.
|
|
*/
|
|
void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
|
|
{
|
|
__call_rcu(head, func, &rcu_bh_ctrlblk);
|
|
}
|
|
EXPORT_SYMBOL_GPL(call_rcu_bh);
|
|
|
|
void rcu_barrier_bh(void)
|
|
{
|
|
struct rcu_synchronize rcu;
|
|
|
|
init_rcu_head_on_stack(&rcu.head);
|
|
init_completion(&rcu.completion);
|
|
/* Will wake me after RCU finished. */
|
|
call_rcu_bh(&rcu.head, wakeme_after_rcu);
|
|
/* Wait for it. */
|
|
wait_for_completion(&rcu.completion);
|
|
destroy_rcu_head_on_stack(&rcu.head);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_barrier_bh);
|
|
|
|
void rcu_barrier_sched(void)
|
|
{
|
|
struct rcu_synchronize rcu;
|
|
|
|
init_rcu_head_on_stack(&rcu.head);
|
|
init_completion(&rcu.completion);
|
|
/* Will wake me after RCU finished. */
|
|
call_rcu_sched(&rcu.head, wakeme_after_rcu);
|
|
/* Wait for it. */
|
|
wait_for_completion(&rcu.completion);
|
|
destroy_rcu_head_on_stack(&rcu.head);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_barrier_sched);
|
|
|
|
/*
|
|
* Spawn the kthread that invokes RCU callbacks.
|
|
*/
|
|
static int __init rcu_spawn_kthreads(void)
|
|
{
|
|
struct sched_param sp;
|
|
|
|
rcu_kthread_task = kthread_run(rcu_kthread, NULL, "rcu_kthread");
|
|
sp.sched_priority = RCU_BOOST_PRIO;
|
|
sched_setscheduler_nocheck(rcu_kthread_task, SCHED_FIFO, &sp);
|
|
return 0;
|
|
}
|
|
early_initcall(rcu_spawn_kthreads);
|