On 5/13/23 4:12 PM, Tian Lan wrote:
> From: Tian Lan <tian.lan@xxxxxxxxxxxx>
>
> The nr_active counter continues to increase over time which causes the
> blk_mq_get_tag to hang until the thread is rescheduled to a different
> core despite there are still tags available.
>
> kernel-stack
>
> INFO: task inboundIOReacto:3014879 blocked for more than 2 seconds
> Not tainted 6.1.15-amd64 #1 Debian 6.1.15~debian11
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:inboundIOReacto state:D stack:0 pid:3014879 ppid:4557 flags:0x00000000
> Call Trace:
> <TASK>
> __schedule+0x351/0xa20
> scheduler+0x5d/0xe0
> io_schedule+0x42/0x70
> blk_mq_get_tag+0x11a/0x2a0
> ? dequeue_task_stop+0x70/0x70
> __blk_mq_alloc_requests+0x191/0x2e0
>
> kprobe output showing RQF_MQ_INFLIGHT bit is not cleared before
> __blk_mq_free_request being called.
>
> 320 320 kworker/29:1H __blk_mq_free_request rq_flags 0x220c0 in-flight 1
> b'__blk_mq_free_request+0x1 [kernel]'
> b'bt_iter+0x50 [kernel]'
> b'blk_mq_queue_tag_busy_iter+0x318 [kernel]'
> b'blk_mq_timeout_work+0x7c [kernel]'
> b'process_one_work+0x1c4 [kernel]'
> b'worker_thread+0x4d [kernel]'
> b'kthread+0xe6 [kernel]'
> b'ret_from_fork+0x1f [kernel]'
>
> Signed-off-by: Tian Lan <tian.lan@xxxxxxxxxxxx>
I think this needs:
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 2e315dc07df0 ("blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter")
tags, but I'm also now confused as to whether the flush handling part
of that patch. Ming, what am I missing in terms of not honoring the
flush ref on put? What happens if two iterators both grab the
flush at the same time, and then subsequently put them?
--
Jens Axboe
