Re: [PATCH] blk-mq: Allow blocking queue tag iter callbacks
From: Keith Busch <hidden>
Date: 2018-09-25 15:47:45
On Tue, Sep 25, 2018 at 08:14:45AM -0700, Bart Van Assche wrote:
On Tue, 2018-09-25 at 08:39 -0600, Keith Busch wrote:quoted
On Tue, Sep 25, 2018 at 10:39:46AM +0800, jianchao.wang wrote:quoted
But the issue is the left part of blk_mq_timeout_work is moved out of protection of q refcount.I'm not sure what you mean by "left part". The only part that isn't outside the reference with this patch is the part Bart pointed out. This looks like it may be fixed by either moving the refcount back up a level to all the callers of blk_mq_queue_tag_busy_iter, or add cancel_work_sync(&q->timeout_work) to __blk_mq_update_nr_hw_queues after the freeze.Hi Keith, How about applying the following (untested) patch on top of your patch?
Yep, this works. I can fold in a v2.
quoted hunk ↗ jump to hunk
diff --git a/block/blk-mq.c b/block/blk-mq.c index 019f9b169887..099e203b5213 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c@@ -851,6 +851,9 @@ static void blk_mq_timeout_work(struct work_struct *work) if (!blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next)) return; + if (!percpu_ref_tryget(&q->q_usage_counter)) + return; + if (next != 0) { mod_timer(&q->timeout, next); } else {@@ -866,6 +869,7 @@ static void blk_mq_timeout_work(struct work_struct *work) blk_mq_tag_idle(hctx); } } + blk_queue_exit(q); }Thanks, Bart.