Commit a12bffeb authored May 31, 2018 by Filippo Muzzini Committed by Jens Axboe May 31, 2018

block, bfq: remove wrong lock in bfq_requests_merged



In bfq_requests_merged(), there is a deadlock because the lock on
bfqq->bfqd->lock is held by the calling function, but the code of
this function tries to grab the lock again.

This deadlock is currently hidden by another bug (fixed by next commit
for this source file), which causes the body of bfq_requests_merged()
to be never executed.

This commit removes the deadlock by removing the lock/unlock pair.

Signed-off-by: Filippo Muzzini <filippo.muzzini@outlook.it>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 04c4950d

block/bfq-iosched.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -1847,7 +1847,6 @@ static void bfq_requests_merged(struct request_queue q, struct request rq,

		if (!RB_EMPTY_NODE(&rq->rb_node))
		goto end;
		spin_lock_irq(&bfqq->bfqd->lock);

		/*
		* If next and rq belong to the same bfq_queue and next is older
		@@ -1872,7 +1871,6 @@ static void bfq_requests_merged(struct request_queue q, struct request rq,
		bfq_remove_request(q, next);
		bfqg_stats_update_io_remove(bfqq_group(bfqq), next->cmd_flags);

		spin_unlock_irq(&bfqq->bfqd->lock);
		end:
		bfqg_stats_update_io_merged(bfqq_group(bfqq), next->cmd_flags);
		}