On 10/26/12 14:00, Bart Van Assche wrote:
> Fix a few race conditions that can be triggered by removing a device:
> [ ... ]
Hello,
I'd like to add the patch below to this series. This is something I came
up with after analyzing why a crash was triggered during an SRP failover
test. One of the functions in the crash call stack was blk_delay_work().
Bart.
[PATCH] 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@xxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Mike Christie <michaelc@xxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
---
block/blk-core.c | 26 +++++---------------------
1 file changed, 5 insertions(+), 21 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index e4f4e06..212c878 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -343,11 +343,11 @@ 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);
@@ -2923,27 +2923,11 @@ 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);
- }
-
+ spin_unlock(q->queue_lock);
}
static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule)
--
1.7.10.4
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