From: Bart Van Assche <bart.vanassche@sandisk.com> To: Jens Axboe <axboe@fb.com> Cc: Christoph Hellwig <hch@lst.de>, James Bottomley <jejb@linux.vnet.ibm.com>, "Martin K. Petersen" <martin.petersen@oracle.com>, Mike Snitzer <snitzer@redhat.com>, Doug Ledford <dledford@redhat.com>, Keith Busch <keith.busch@intel.com>, "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>, "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>, "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>, "linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org> Subject: [PATCH 2/9] dm: Fix a race condition related to stopping and starting queues Date: Mon, 26 Sep 2016 11:26:50 -0700 [thread overview] Message-ID: <ba8ddc16-b709-e7fb-1120-b6e1bd393540@sandisk.com> (raw) In-Reply-To: <7948dbb8-6333-dc62-2673-4da35b4dfdbc@sandisk.com> Ensure that all ongoing dm_mq_queue_rq() and dm_mq_requeue_request() calls have stopped before setting the "queue stopped" flag. This allows to remove the "queue stopped" test from dm_mq_queue_rq() and dm_mq_requeue_request(). This patch fixes a race condition because dm_mq_queue_rq() is called without holding the queue lock and hence BLK_MQ_S_STOPPED can be set at any time while dm_mq_queue_rq() is in progress. Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com> Cc: Mike Snitzer <snitzer@redhat.com> --- drivers/md/dm-rq.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-) diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index 182b679..1b7a65e 100644 --- a/drivers/md/dm-rq.c +++ b/drivers/md/dm-rq.c @@ -116,9 +116,12 @@ static void dm_mq_stop_queue(struct request_queue *q) queue_flag_set(QUEUE_FLAG_STOPPED, q); spin_unlock_irqrestore(q->queue_lock, flags); + /* Wait until dm_mq_queue_rq() has finished. */ + blk_quiesce_queue(q); /* Avoid that requeuing could restart the queue. */ blk_mq_cancel_requeue_work(q); blk_mq_stop_hw_queues(q); + blk_resume_queue(q); } void dm_stop_queue(struct request_queue *q) @@ -901,17 +904,6 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx, dm_put_live_table(md, srcu_idx); } - /* - * On suspend dm_stop_queue() handles stopping the blk-mq - * request_queue BUT: even though the hw_queues are marked - * BLK_MQ_S_STOPPED at that point there is still a race that - * is allowing block/blk-mq.c to call ->queue_rq against a - * hctx that it really shouldn't. The following check guards - * against this rarity (albeit _not_ race-free). - */ - if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state))) - return BLK_MQ_RQ_QUEUE_BUSY; - if (ti->type->busy && ti->type->busy(ti)) return BLK_MQ_RQ_QUEUE_BUSY; -- 2.10.0
WARNING: multiple messages have this Message-ID (diff)
From: bart.vanassche@sandisk.com (Bart Van Assche) Subject: [PATCH 2/9] dm: Fix a race condition related to stopping and starting queues Date: Mon, 26 Sep 2016 11:26:50 -0700 [thread overview] Message-ID: <ba8ddc16-b709-e7fb-1120-b6e1bd393540@sandisk.com> (raw) In-Reply-To: <7948dbb8-6333-dc62-2673-4da35b4dfdbc@sandisk.com> Ensure that all ongoing dm_mq_queue_rq() and dm_mq_requeue_request() calls have stopped before setting the "queue stopped" flag. This allows to remove the "queue stopped" test from dm_mq_queue_rq() and dm_mq_requeue_request(). This patch fixes a race condition because dm_mq_queue_rq() is called without holding the queue lock and hence BLK_MQ_S_STOPPED can be set at any time while dm_mq_queue_rq() is in progress. Signed-off-by: Bart Van Assche <bart.vanassche at sandisk.com> Cc: Mike Snitzer <snitzer at redhat.com> --- drivers/md/dm-rq.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-) diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index 182b679..1b7a65e 100644 --- a/drivers/md/dm-rq.c +++ b/drivers/md/dm-rq.c @@ -116,9 +116,12 @@ static void dm_mq_stop_queue(struct request_queue *q) queue_flag_set(QUEUE_FLAG_STOPPED, q); spin_unlock_irqrestore(q->queue_lock, flags); + /* Wait until dm_mq_queue_rq() has finished. */ + blk_quiesce_queue(q); /* Avoid that requeuing could restart the queue. */ blk_mq_cancel_requeue_work(q); blk_mq_stop_hw_queues(q); + blk_resume_queue(q); } void dm_stop_queue(struct request_queue *q) @@ -901,17 +904,6 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx, dm_put_live_table(md, srcu_idx); } - /* - * On suspend dm_stop_queue() handles stopping the blk-mq - * request_queue BUT: even though the hw_queues are marked - * BLK_MQ_S_STOPPED at that point there is still a race that - * is allowing block/blk-mq.c to call ->queue_rq against a - * hctx that it really shouldn't. The following check guards - * against this rarity (albeit _not_ race-free). - */ - if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state))) - return BLK_MQ_RQ_QUEUE_BUSY; - if (ti->type->busy && ti->type->busy(ti)) return BLK_MQ_RQ_QUEUE_BUSY; -- 2.10.0
next prev parent reply other threads:[~2016-09-26 18:27 UTC|newest] Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-09-26 18:25 [PATCH 0/9] Introduce blk_quiesce_queue() and blk_resume_queue() Bart Van Assche 2016-09-26 18:25 ` Bart Van Assche 2016-09-26 18:26 ` [PATCH 1/9] blk-mq: Introduce blk_mq_queue_stopped() Bart Van Assche 2016-09-26 18:26 ` Bart Van Assche 2016-09-26 18:26 ` Bart Van Assche 2016-09-27 6:20 ` Hannes Reinecke 2016-09-27 6:20 ` Hannes Reinecke 2016-09-27 7:38 ` Johannes Thumshirn 2016-09-27 7:38 ` Johannes Thumshirn 2016-09-27 7:38 ` Johannes Thumshirn 2016-09-26 18:26 ` Bart Van Assche [this message] 2016-09-26 18:26 ` [PATCH 2/9] dm: Fix a race condition related to stopping and starting queues Bart Van Assche 2016-09-27 6:21 ` Hannes Reinecke 2016-09-27 6:21 ` Hannes Reinecke 2016-09-27 6:21 ` Hannes Reinecke 2016-09-27 7:47 ` Johannes Thumshirn 2016-09-27 7:47 ` Johannes Thumshirn 2016-09-27 7:47 ` Johannes Thumshirn 2016-09-26 18:27 ` [PATCH 3/9] [RFC] nvme: Use BLK_MQ_S_STOPPED instead of QUEUE_FLAG_STOPPED in blk-mq code Bart Van Assche 2016-09-26 18:27 ` Bart Van Assche 2016-09-26 18:27 ` Bart Van Assche 2016-09-26 18:27 ` [PATCH 4/9] block: Move blk_freeze_queue() and blk_unfreeze_queue() code Bart Van Assche 2016-09-26 18:27 ` Bart Van Assche 2016-09-27 6:26 ` Hannes Reinecke 2016-09-27 6:26 ` Hannes Reinecke 2016-09-27 6:26 ` Hannes Reinecke 2016-09-27 7:52 ` Johannes Thumshirn 2016-09-27 7:52 ` Johannes Thumshirn 2016-09-27 7:52 ` Johannes Thumshirn 2016-09-26 18:27 ` [PATCH 5/9] block: Extend blk_freeze_queue_start() to the non-blk-mq path Bart Van Assche 2016-09-26 18:27 ` Bart Van Assche 2016-09-26 18:27 ` Bart Van Assche 2016-09-27 7:50 ` Johannes Thumshirn 2016-09-27 7:50 ` Johannes Thumshirn 2016-09-27 7:50 ` Johannes Thumshirn 2016-09-27 13:22 ` Ming Lei 2016-09-27 13:22 ` Ming Lei 2016-09-27 14:42 ` Bart Van Assche 2016-09-27 14:42 ` Bart Van Assche 2016-09-27 14:42 ` Bart Van Assche 2016-09-27 15:55 ` Bart Van Assche 2016-09-27 15:55 ` Bart Van Assche 2016-09-27 15:55 ` Bart Van Assche 2016-09-26 18:28 ` [PATCH 6/9] block: Rename mq_freeze_wq and mq_freeze_depth Bart Van Assche 2016-09-26 18:28 ` Bart Van Assche 2016-09-27 7:51 ` Johannes Thumshirn 2016-09-27 7:51 ` Johannes Thumshirn 2016-09-27 7:51 ` Johannes Thumshirn 2016-09-26 18:28 ` [PATCH 7/9] blk-mq: Introduce blk_quiesce_queue() and blk_resume_queue() Bart Van Assche 2016-09-26 18:28 ` Bart Van Assche 2016-09-26 18:28 ` [PATCH 8/9] SRP transport: Port srp_wait_for_queuecommand() to scsi-mq Bart Van Assche 2016-09-26 18:28 ` Bart Van Assche 2016-09-26 18:28 ` [PATCH 9/9] [RFC] nvme: Fix a race condition Bart Van Assche 2016-09-26 18:28 ` Bart Van Assche 2016-09-27 16:31 ` Steve Wise 2016-09-27 16:31 ` Steve Wise 2016-09-27 16:31 ` Steve Wise 2016-09-27 16:43 ` Bart Van Assche 2016-09-27 16:43 ` Bart Van Assche 2016-09-27 16:43 ` Bart Van Assche 2016-09-27 16:56 ` James Bottomley 2016-09-27 16:56 ` James Bottomley 2016-09-27 17:09 ` Bart Van Assche 2016-09-27 17:09 ` Bart Van Assche 2016-09-27 17:09 ` Bart Van Assche 2016-09-28 14:23 ` Steve Wise 2016-09-28 14:23 ` Steve Wise 2016-09-28 14:23 ` Steve Wise 2016-09-27 16:56 ` Steve Wise 2016-09-27 16:56 ` Steve Wise 2016-09-27 16:56 ` Steve Wise 2016-09-26 18:33 ` [PATCH 0/9] Introduce blk_quiesce_queue() and blk_resume_queue() Mike Snitzer 2016-09-26 18:33 ` Mike Snitzer 2016-09-26 18:33 ` Mike Snitzer 2016-09-26 18:46 ` Bart Van Assche 2016-09-26 18:46 ` Bart Van Assche 2016-09-26 18:46 ` Bart Van Assche 2016-09-26 22:26 ` Bart Van Assche 2016-09-26 22:26 ` Bart Van Assche 2016-09-26 22:26 ` Bart Van Assche 2016-10-11 16:27 ` Laurence Oberman 2016-10-11 16:27 ` Laurence Oberman
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