From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: [PATCH v6 05/13] block: Make blk_cleanup_queue() wait until request_fn finished Date: Wed, 28 Nov 2012 13:46:45 +0100 Message-ID: <50B607B5.7020808@acm.org> References: <50B60619.4080406@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from jacques.telenet-ops.be ([195.130.132.50]:46499 "EHLO jacques.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754291Ab2K1Mqq (ORCPT ); Wed, 28 Nov 2012 07:46:46 -0500 In-Reply-To: <50B60619.4080406@acm.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org Cc: linux-scsi , James Bottomley , Mike Christie , Jens Axboe , Tejun Heo , Chanho Min , Hannes Reinecke Some request_fn implementations, e.g. scsi_request_fn(), unlock the queue lock internally. This may result in multiple threads executing request_fn for the same queue simultaneously. Keep track of the number of active request_fn calls and make sure that blk_cleanup_queue() waits until all active request_fn invocations have finished. A block driver may start cleaning up resources needed by its request_fn as soon as blk_cleanup_queue() finished, so blk_cleanup_queue() must wait for all outstanding request_fn invocations to finish. Signed-off-by: Bart Van Assche Reported-by: Chanho Min Cc: James Bottomley Cc: Mike Christie Cc: Jens Axboe Cc: Tejun Heo --- block/blk-core.c | 10 ++++++++++ include/linux/blkdev.h | 6 ++++++ 2 files changed, 16 insertions(+) diff --git a/block/blk-core.c b/block/blk-core.c index 12deca9..4d09af4 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -309,7 +309,16 @@ inline void __blk_run_queue_uncond(struct request_queue *q) if (unlikely(blk_queue_dead(q))) return; + /* + * Some request_fn implementations, e.g. scsi_request_fn(), unlock + * the queue lock internally. As a result multiple threads may be + * running such a request function concurrently. Keep track of the + * number of active request_fn invocations such that blk_drain_queue() + * can wait until all these request_fn calls have finished. + */ + q->request_fn_active++; q->request_fn(q); + q->request_fn_active--; } /** @@ -408,6 +417,7 @@ static void __blk_drain_queue(struct request_queue *q, bool drain_all) __blk_run_queue(q); drain |= q->nr_rqs_elvpriv; + drain |= q->request_fn_active; /* * Unfortunately, requests are queued at and tracked from diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 8bc46c2..c9d233e 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -378,6 +378,12 @@ struct request_queue { unsigned int nr_sorted; unsigned int in_flight[2]; + /* + * Number of active block driver functions for which blk_drain_queue() + * must wait. Must be incremented around functions that unlock the + * queue_lock internally, e.g. scsi_request_fn(). + */ + unsigned int request_fn_active; unsigned int rq_timeout; struct timer_list timeout; -- 1.7.10.4