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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>
This commit is contained in:
Lai Jiangshan 2013-02-06 18:04:53 -08:00 committed by Tejun Heo
parent 6be195886a
commit 038366c5cf
1 changed files with 6 additions and 10 deletions
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16
kernel/workqueue.c
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@ -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 (find_worker_executing_work(pool, work))
ret |= WORK_BUSY_RUNNING;
spin_unlock_irqrestore(&pool->lock, flags);
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;
}