From 3d492c2e0146ccaad08c7cbe16e2e229328b5e79 Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Fri, 10 Feb 2017 10:32:34 -0800 Subject: [PATCH] blk-mq-sched: don't hold queue_lock when calling exit_icq None of the other blk-mq elevator hooks are called with this lock held. Additionally, it can lead to circular locking dependencies between queue_lock and the private scheduler lock. Reported-by: Paolo Valente Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe --- block/blk-ioc.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/block/blk-ioc.c b/block/blk-ioc.c index fe186a9eade9..b12f9c87b4c3 100644 --- a/block/blk-ioc.c +++ b/block/blk-ioc.c @@ -35,7 +35,10 @@ static void icq_free_icq_rcu(struct rcu_head *head) kmem_cache_free(icq->__rcu_icq_cache, icq); } -/* Exit an icq. Called with both ioc and q locked. */ +/* + * Exit an icq. Called with both ioc and q locked for sq, only ioc locked for + * mq. + */ static void ioc_exit_icq(struct io_cq *icq) { struct elevator_type *et = icq->q->elevator->type; @@ -166,6 +169,7 @@ EXPORT_SYMBOL(put_io_context); */ void put_io_context_active(struct io_context *ioc) { + struct elevator_type *et; unsigned long flags; struct io_cq *icq; @@ -184,13 +188,19 @@ retry: hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) { if (icq->flags & ICQ_EXITED) continue; - if (spin_trylock(icq->q->queue_lock)) { + + et = icq->q->elevator->type; + if (et->uses_mq) { ioc_exit_icq(icq); - spin_unlock(icq->q->queue_lock); } else { - spin_unlock_irqrestore(&ioc->lock, flags); - cpu_relax(); - goto retry; + if (spin_trylock(icq->q->queue_lock)) { + ioc_exit_icq(icq); + spin_unlock(icq->q->queue_lock); + } else { + spin_unlock_irqrestore(&ioc->lock, flags); + cpu_relax(); + goto retry; + } } } spin_unlock_irqrestore(&ioc->lock, flags); -- 2.30.2