Commit 1f1f642e authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

make cancel_xxx_work_sync() return a boolean 



Change cancel_work_sync() and cancel_delayed_work_sync() to return a boolean
indicating whether the work was actually cancelled.  A zero return value means
that the work was not pending/queued.

Without that kind of change it is not possible to avoid flush_workqueue()
sometimes, see the next patch as an example.

Also, this patch unifies both functions and kills the (unlikely) busy-wait
loop.

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Acked-by: default avatarJarek Poplawski <jarkao2@o2.pl>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f5a421a4

include/linux/workqueue.h

+2 −2
Original line number Diff line number Diff line
@@ -148,7 +148,7 @@ extern int keventd_up(void); 
extern void init_workqueues(void);

int execute_in_process_context(work_func_t fn, struct execute_work *);



extern void cancel_work_sync(struct work_struct *work);

extern int cancel_work_sync(struct work_struct *work);



/*

 * Kill off a pending schedule_delayed_work().  Note that the work callback
@@ -166,7 +166,7 @@ static inline int cancel_delayed_work(struct delayed_work *work) 
	return ret;

}



extern void cancel_delayed_work_sync(struct delayed_work *work);

extern int cancel_delayed_work_sync(struct delayed_work *work);



/* Obsolete. use cancel_delayed_work_sync() */

static inline

kernel/workqueue.c

+27 −14
Original line number Diff line number Diff line
@@ -382,16 +382,16 @@ void fastcall flush_workqueue(struct workqueue_struct *wq) 
EXPORT_SYMBOL_GPL(flush_workqueue);



/*

 * Upon a successful return, the caller "owns" WORK_STRUCT_PENDING bit,

 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,

 * so this work can't be re-armed in any way.

 */

static int try_to_grab_pending(struct work_struct *work)

{

	struct cpu_workqueue_struct *cwq;

	int ret = 0;

	int ret = -1;



	if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))

		return 1;

		return 0;



	/*

	 * The queueing is in progress, or it is already queued. Try to
@@ -457,10 +457,28 @@ static void wait_on_work(struct work_struct *work) 
		wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);

}



static int __cancel_work_timer(struct work_struct *work,

				struct timer_list* timer)

{

	int ret;



	do {

		ret = (timer && likely(del_timer(timer)));

		if (!ret)

			ret = try_to_grab_pending(work);

		wait_on_work(work);

	} while (unlikely(ret < 0));



	work_clear_pending(work);

	return ret;

}



/**

 * cancel_work_sync - block until a work_struct's callback has terminated

 * @work: the work which is to be flushed

 *

 * Returns true if @work was pending.

 *

 * cancel_work_sync() will cancel the work if it is queued. If the work's

 * callback appears to be running, cancel_work_sync() will block until it

 * has completed.
@@ -476,12 +494,9 @@ static void wait_on_work(struct work_struct *work) 
 * The caller must ensure that workqueue_struct on which this work was last

 * queued can't be destroyed before this function returns.

 */

void cancel_work_sync(struct work_struct *work)

int cancel_work_sync(struct work_struct *work)

{

	while (!try_to_grab_pending(work))

		cpu_relax();

	wait_on_work(work);

	work_clear_pending(work);

	return __cancel_work_timer(work, NULL);

}

EXPORT_SYMBOL_GPL(cancel_work_sync);
@@ -489,16 +504,14 @@ EXPORT_SYMBOL_GPL(cancel_work_sync); 
 * cancel_delayed_work_sync - reliably kill off a delayed work.

 * @dwork: the delayed work struct

 *

 * Returns true if @dwork was pending.

 *

 * It is possible to use this function if @dwork rearms itself via queue_work()

 * or queue_delayed_work(). See also the comment for cancel_work_sync().

 */

void cancel_delayed_work_sync(struct delayed_work *dwork)

int cancel_delayed_work_sync(struct delayed_work *dwork)

{

	while (!del_timer(&dwork->timer) &&

	       !try_to_grab_pending(&dwork->work))

		cpu_relax();

	wait_on_work(&dwork->work);

	work_clear_pending(&dwork->work);

	return __cancel_work_timer(&dwork->work, &dwork->timer);

}

EXPORT_SYMBOL(cancel_delayed_work_sync);

CRA Git | Maintained and supported by SUSTech CRA and CCSE