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workqueue: reorganize try_to_grab_pending() and __cancel_timer_work() 

* Use bool @is_dwork instead of @timer and let try_to_grab_pending()
  use to_delayed_work() to determine the delayed_work address.

* Move timer handling from __cancel_work_timer() to
  try_to_grab_pending().

* Make try_to_grab_pending() use -EAGAIN instead of -1 for
  busy-looping and drop the ret local variable.

* Add proper function comment to try_to_grab_pending().

This makes the code a bit easier to understand and will ease further
changes.  This patch doesn't make any functional change.

v2: Use @is_dwork instead of @timer.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2012-08-03 10:30:46 -07:00
parent 7beb2edf44
commit 36e227d242
1 changed files with 32 additions and 15 deletions
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47
kernel/workqueue.c
View File

@ -1004,15 +1004,33 @@ static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
complete(&cwq->wq->first_flusher->done);
}
/*
* Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
* so this work can't be re-armed in any way.
/**
* try_to_grab_pending - steal work item from worklist
* @work: work item to steal
* @is_dwork: @work is a delayed_work
*
* Try to grab PENDING bit of @work. This function can handle @work in any
* stable state - idle, on timer or on worklist. Return values are
*
* 1 if @work was pending and we successfully stole PENDING
* 0 if @work was idle and we claimed PENDING
* -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
*
* On >= 0 return, the caller owns @work's PENDING bit.
*/
static int try_to_grab_pending(struct work_struct *work)
static int try_to_grab_pending(struct work_struct *work, bool is_dwork)
{
struct global_cwq *gcwq;
int ret = -1;
/* try to steal the timer if it exists */
if (is_dwork) {
struct delayed_work *dwork = to_delayed_work(work);
if (likely(del_timer(&dwork->timer)))
return 1;
}
/* try to claim PENDING the normal way */
if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
return 0;
@ -1022,7 +1040,7 @@ static int try_to_grab_pending(struct work_struct *work)
*/
gcwq = get_work_gcwq(work);
if (!gcwq)
return ret;
return -EAGAIN;
spin_lock_irq(&gcwq->lock);
if (!list_empty(&work->entry)) {
@ -1038,12 +1056,14 @@ static int try_to_grab_pending(struct work_struct *work)
cwq_dec_nr_in_flight(get_work_cwq(work),
get_work_color(work),
*work_data_bits(work) & WORK_STRUCT_DELAYED);
ret = 1;
spin_unlock_irq(&gcwq->lock);
return 1;
}
}
spin_unlock_irq(&gcwq->lock);
return ret;
return -EAGAIN;
}
/**
@ -2817,15 +2837,12 @@ bool flush_work_sync(struct work_struct *work)
}
EXPORT_SYMBOL_GPL(flush_work_sync);
static bool __cancel_work_timer(struct work_struct *work,
struct timer_list* timer)
static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
{
int ret;
do {
ret = (timer && likely(del_timer(timer)));
if (!ret)
ret = try_to_grab_pending(work);
ret = try_to_grab_pending(work, is_dwork);
wait_on_work(work);
} while (unlikely(ret < 0));
@ -2853,7 +2870,7 @@ static bool __cancel_work_timer(struct work_struct *work,
*/
bool cancel_work_sync(struct work_struct *work)
{
return __cancel_work_timer(work, NULL);
return __cancel_work_timer(work, false);
}
EXPORT_SYMBOL_GPL(cancel_work_sync);
@ -2914,7 +2931,7 @@ EXPORT_SYMBOL(flush_delayed_work_sync);
*/
bool cancel_delayed_work_sync(struct delayed_work *dwork)
{
return __cancel_work_timer(&dwork->work, &dwork->timer);
return __cancel_work_timer(&dwork->work, true);
}
EXPORT_SYMBOL(cancel_delayed_work_sync);