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blk-mq: fix deadlock in blk_mq_register_disk() error path 

If we fail registering any of the hardware queues, we call
into blk_mq_unregister_disk() with the hotplug mutex already
held. Since blk_mq_unregister_disk() attempts to acquire the
same mutex, we end up in a less than happy place.

Reported-by: Jinpu Wang <jinpu.wang@profitbricks.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2016-08-02 08:45:44 -06:00
parent 6d25ec147e
commit c0f3fd2b38
1 changed files with 8 additions and 4 deletions
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12
block/blk-mq-sysfs.c
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@ -380,15 +380,13 @@ static int blk_mq_register_hctx(struct blk_mq_hw_ctx *hctx)
return ret;
}
void blk_mq_unregister_disk(struct gendisk *disk)
static void __blk_mq_unregister_disk(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
struct blk_mq_hw_ctx *hctx;
struct blk_mq_ctx *ctx;
int i, j;
blk_mq_disable_hotplug();
queue_for_each_hw_ctx(q, hctx, i) {
blk_mq_unregister_hctx(hctx);
@ -405,6 +403,12 @@ void blk_mq_unregister_disk(struct gendisk *disk)
kobject_put(&disk_to_dev(disk)->kobj);
q->mq_sysfs_init_done = false;
}
void blk_mq_unregister_disk(struct gendisk *disk)
{
blk_mq_disable_hotplug();
__blk_mq_unregister_disk(disk);
blk_mq_enable_hotplug();
}
@ -450,7 +454,7 @@ int blk_mq_register_disk(struct gendisk *disk)
}
if (ret)
blk_mq_unregister_disk(disk);
__blk_mq_unregister_disk(disk);
else
q->mq_sysfs_init_done = true;
out: