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>
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 7e11334..a229a56 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3443,8 +3443,6 @@
* 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 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;
}
