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make cancel_xxx_work_sync() return a boolean

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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: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Jarek Poplawski <jarkao2@o2.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2007-07-15 23:41:44 -07:00 committed by Linus Torvalds
parent f5a421a450
commit 1f1f642e2f
2 changed files with 29 additions and 16 deletions
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4
include/linux/workqueue.h
View file

@ -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

41
kernel/workqueue.c
View file

@ -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);