Commit 038366c5 authored Feb 06, 2013 by Lai Jiangshan Committed by Tejun Heo Feb 06, 2013

workqueue: make work_busy() test WORK_STRUCT_PENDING first



Currently, work_busy() first tests whether the work has a pool
associated with it and if not, considers it idle.  This works fine
even for delayed_work.work queued on timer, as __queue_delayed_work()
sets cwq on delayed_work.work - a queued delayed_work always has its
cwq and thus pool associated with it.

However, we're about to update delayed_work queueing and this won't
hold.  Update work_busy() such that it tests WORK_STRUCT_PENDING
before the associated pool.  This doesn't make any noticeable behavior
difference now.

With work_pending() test moved, the function read a lot better with
"if (!pool)" test flipped to positive.  Flip it.

While at it, lose the comment about now non-existent reentrant
workqueues.

tj: Reorganized the function and rewrote the description.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

parent 6be19588

kernel/workqueue.c

+6 −10

Original line number	Diff line number	Diff line
		@@ -3443,8 +3443,6 @@ EXPORT_SYMBOL_GPL(workqueue_congested);
		* Test whether @work is currently pending or running. There is no
		* synchronization around this function and the test result is
		* unreliable and only useful as advisory hints or for debugging.
		* Especially for reentrant wqs, the pending state might hide the
		* running state.
		*
		* RETURNS:
		* OR'd bitmask of WORK_BUSY_* bits.
		@@ -3455,17 +3453,15 @@ unsigned int work_busy(struct work_struct *work)
		unsigned long flags;
		unsigned int ret = 0;

		if (!pool)
		return 0;

		spin_lock_irqsave(&pool->lock, flags);

		if (work_pending(work))
		ret \|= WORK_BUSY_PENDING;

		if (pool) {
		spin_lock_irqsave(&pool->lock, flags);
		if (find_worker_executing_work(pool, work))
		ret \|= WORK_BUSY_RUNNING;

		spin_unlock_irqrestore(&pool->lock, flags);
		}

		return ret;
		}

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