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Commit fd450b73 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

[PATCH] timers: introduce try_to_del_timer_sync() 



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: default avatarOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 55c888d6

include/linux/timer.h

+3 −1
Original line number Diff line number Diff line
@@ -76,8 +76,10 @@ 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 try_to_del_timer_sync(t)	del_timer(t)

# define del_timer_sync(t)		del_timer(t)

#endif

kernel/timer.c

+33 −20
Original line number Diff line number Diff line
@@ -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
@@ -384,29 +412,14 @@ 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);



	for (;;) {

		int ret = try_to_del_timer_sync(timer);

		if (ret >= 0)

			return ret;

	}

}



EXPORT_SYMBOL(del_timer_sync);

#endif