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[PATCH] timers: introduce try_to_del_timer_sync()

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This patch splits del_timer_sync() into 2 functions.  The new one,
try_to_del_timer_sync(), returns -1 when it hits executing timer.

It can be used in interrupt context, or when the caller hold locks which
can prevent completion of the timer's handler.

NOTE.  Currently it can't be used in interrupt context in UP case, because
->running_timer is used only with CONFIG_SMP.

Should the need arise, it is possible to kill #ifdef CONFIG_SMP in
set_running_timer(), it is cheap.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Oleg Nesterov 2005-06-23 00:08:59 -07:00 committed by Linus Torvalds
parent 55c888d6d0
commit fd450b7318
2 changed files with 36 additions and 21 deletions
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4
include/linux/timer.h
View file

@ -76,9 +76,11 @@ static inline void add_timer(struct timer_list * timer)
}
#ifdef CONFIG_SMP
extern int try_to_del_timer_sync(struct timer_list *timer);
extern int del_timer_sync(struct timer_list *timer);
#else
# define del_timer_sync(t) del_timer(t)
# define try_to_del_timer_sync(t) del_timer(t)
# define del_timer_sync(t) del_timer(t)
#endif
#define del_singleshot_timer_sync(t) del_timer_sync(t)

53
kernel/timer.c
View file

@ -365,6 +365,34 @@ int del_timer(struct timer_list *timer)
EXPORT_SYMBOL(del_timer);
#ifdef CONFIG_SMP
/*
* This function tries to deactivate a timer. Upon successful (ret >= 0)
* exit the timer is not queued and the handler is not running on any CPU.
*
* It must not be called from interrupt contexts.
*/
int try_to_del_timer_sync(struct timer_list *timer)
{
timer_base_t *base;
unsigned long flags;
int ret = -1;
base = lock_timer_base(timer, &flags);
if (base->running_timer == timer)
goto out;
ret = 0;
if (timer_pending(timer)) {
detach_timer(timer, 1);
ret = 1;
}
out:
spin_unlock_irqrestore(&base->lock, flags);
return ret;
}
/***
* del_timer_sync - deactivate a timer and wait for the handler to finish.
* @timer: the timer to be deactivated
@ -384,28 +412,13 @@ EXPORT_SYMBOL(del_timer);
*/
int del_timer_sync(struct timer_list *timer)
{
timer_base_t *base;
unsigned long flags;
int ret = -1;
check_timer(timer);
do {
base = lock_timer_base(timer, &flags);
if (base->running_timer == timer)
goto unlock;
ret = 0;
if (timer_pending(timer)) {
detach_timer(timer, 1);
ret = 1;
}
unlock:
spin_unlock_irqrestore(&base->lock, flags);
} while (ret < 0);
return ret;
for (;;) {
int ret = try_to_del_timer_sync(timer);
if (ret >= 0)
return ret;
}
}
EXPORT_SYMBOL(del_timer_sync);