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block: Avoid scheduling delayed work on a dead queue 

Running a queue must continue after it has been marked dying until
it has been marked dead. So the function blk_run_queue_async() must
not schedule delayed work after blk_cleanup_queue() has marked a queue
dead. Hence add a test for that queue state in blk_run_queue_async()
and make sure that queue_unplugged() invokes that function with the
queue lock held. This avoids that the queue state can change after
it has been tested and before mod_delayed_work() is invoked. Drop
the queue dying test in queue_unplugged() since it is now
superfluous: __blk_run_queue() already tests whether or not the
queue is dead.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2012-11-28 13:45:56 +01:00 committed by Jens Axboe
parent c246e80d86
commit 704605711e
1 changed files with 9 additions and 24 deletions
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27
block/blk-core.c
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@ -219,10 +219,11 @@ static void blk_delay_work(struct work_struct *work)
* Description:
* Sometimes queueing needs to be postponed for a little while, to allow
* resources to come back. This function will make sure that queueing is
* restarted around the specified time.
* restarted around the specified time. Queue lock must be held.
*/
void blk_delay_queue(struct request_queue *q, unsigned long msecs)
{
if (likely(!blk_queue_dead(q)))
queue_delayed_work(kblockd_workqueue, &q->delay_work,
msecs_to_jiffies(msecs));
}
@ -334,11 +335,11 @@ EXPORT_SYMBOL(__blk_run_queue);
*
* Description:
* Tells kblockd to perform the equivalent of @blk_run_queue on behalf
* of us.
* of us. The caller must hold the queue lock.
*/
void blk_run_queue_async(struct request_queue *q)
{
if (likely(!blk_queue_stopped(q)))
if (likely(!blk_queue_stopped(q) && !blk_queue_dead(q)))
mod_delayed_work(kblockd_workqueue, &q->delay_work, 0);
}
EXPORT_SYMBOL(blk_run_queue_async);
@ -2913,27 +2914,11 @@ static void queue_unplugged(struct request_queue *q, unsigned int depth,
{
trace_block_unplug(q, depth, !from_schedule);
/*
* Don't mess with a dying queue.
*/
if (unlikely(blk_queue_dying(q))) {
spin_unlock(q->queue_lock);
return;
}
/*
* If we are punting this to kblockd, then we can safely drop
* the queue_lock before waking kblockd (which needs to take
* this lock).
*/
if (from_schedule) {
spin_unlock(q->queue_lock);
if (from_schedule)
blk_run_queue_async(q);
} else {
else
__blk_run_queue(q);
spin_unlock(q->queue_lock);
}
}
static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule)