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authorAkinobu Mita <akinobu.mita@gmail.com>2015-09-27 02:09:22 +0900
committerJens Axboe <axboe@fb.com>2015-09-29 11:32:48 -0600
commit0e6263682014d480b8d7b8c10287f4536066b54f (patch)
tree6ebd842a4a9ef717cfc4a05c99fddede9fb4328e
parenta723bab3d7529133f71fc8a5e96f86e3639a0d13 (diff)
blk-mq: fix q->mq_usage_counter access race
CPU hotplug handling for blk-mq (blk_mq_queue_reinit) accesses q->mq_usage_counter while freezing all request queues in all_q_list. On the other hand, q->mq_usage_counter is deinitialized in blk_mq_free_queue() before deleting the queue from all_q_list. So if CPU hotplug event occurs in the window, percpu_ref_kill() is called with q->mq_usage_counter which has already been marked dead, and it triggers warning. Fix it by deleting the queue from all_q_list earlier than destroying q->mq_usage_counter. Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Reviewed-by: Ming Lei <tom.leiming@gmail.com> Cc: Ming Lei <tom.leiming@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
-rw-r--r--block/blk-mq.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 92648d8d6a4a..3a39184e82e5 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2067,15 +2067,16 @@ void blk_mq_free_queue(struct request_queue *q)
{
struct blk_mq_tag_set *set = q->tag_set;
+ mutex_lock(&all_q_mutex);
+ list_del_init(&q->all_q_node);
+ mutex_unlock(&all_q_mutex);
+
blk_mq_del_queue_tag_set(q);
blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
blk_mq_free_hw_queues(q, set);
percpu_ref_exit(&q->mq_usage_counter);
- mutex_lock(&all_q_mutex);
- list_del_init(&q->all_q_node);
- mutex_unlock(&all_q_mutex);
}
/* Basically redo blk_mq_init_queue with queue frozen */