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| author | Ming Lei <tom.leiming@gmail.com> | 2017-03-27 20:06:56 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2017-03-29 08:03:42 -0600 |
| commit | 5ed61d3f08d44937859dc537c5362ca293c98b04 (patch) | |
| tree | 02802c310ece8ac247bb016c5d58555612eea76e /block/blk-core.c | |
| parent | d9d149a39690184f63d74e3425c1e90b1d7e67d6 (diff) | |
| download | lwn-5ed61d3f08d44937859dc537c5362ca293c98b04.tar.gz lwn-5ed61d3f08d44937859dc537c5362ca293c98b04.zip | |
block: add a read barrier in blk_queue_enter()
Without the barrier, reading DEAD flag of .q_usage_counter
and reading .mq_freeze_depth may be reordered, then the
following wait_event_interruptible() may never return.
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-core.c')
| -rw-r--r-- | block/blk-core.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/block/blk-core.c b/block/blk-core.c index 4234332aa23c..6373febc7716 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -669,6 +669,15 @@ int blk_queue_enter(struct request_queue *q, bool nowait) if (nowait) return -EBUSY; + /* + * read pair of barrier in blk_mq_freeze_queue_start(), + * we need to order reading __PERCPU_REF_DEAD flag of + * .q_usage_counter and reading .mq_freeze_depth, + * otherwise the following wait may never return if the + * two reads are reordered. + */ + smp_rmb(); + ret = wait_event_interruptible(q->mq_freeze_wq, !atomic_read(&q->mq_freeze_depth) || blk_queue_dying(q)); |