[PATCH 1/6] blk-mq: make blk_mq_stop_hw_queue() reliably block queue processing

[Tejun Heo <tj@kernel.org>]

blk_mq_stop_hw_queue() has the following two issues.

* BLK_MQ_S_STOPPED should be set before canceling the work items;
  otherwise, a new instance may proceed beyond STOPPED checking
  inbetween.

* cancel_delayed_work() doesn't do anything to work instance already
  executing.  Use cancel_delayed_work_sync() to ensure that the
  currently in-flight one is finished.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Nicholas A. Bellinger <nab@linux-iscsi.org>
---
 block/blk-mq.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index e11f5f8..4787c3d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -862,9 +862,9 @@ EXPORT_SYMBOL(blk_mq_run_queues);
 
 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
 {
-	cancel_delayed_work(&hctx->run_work);
-	cancel_delayed_work(&hctx->delay_work);
 	set_bit(BLK_MQ_S_STOPPED, &hctx->state);
+	cancel_delayed_work_sync(&hctx->run_work);
+	cancel_delayed_work_sync(&hctx->delay_work);
 }
 EXPORT_SYMBOL(blk_mq_stop_hw_queue);
 
-- 
1.9.3