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Commit 24faf6f6 authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
Browse files

block: Make blk_cleanup_queue() wait until request_fn finished 



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: default avatarBart Van Assche <bvanassche@acm.org>
Reported-by: default avatarChanho Min <chanho.min@lge.com>
Cc: James Bottomley <JBottomley@Parallels.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 70460571

block/blk-core.c

+10 −0
Original line number Diff line number Diff line
@@ -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

include/linux/blkdev.h

+6 −0
Original line number Diff line number Diff line
@@ -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;