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Commit 36e227d2 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
parent 7beb2edf

kernel/workqueue.c

+32 −15
Original line number Diff line number Diff line
@@ -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);