Hello Tian, On Sat, May 13, 2023 at 03:05:34PM -0400, 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. RQF_MQ_INFLIGHT won't be cleared when the request is freed normally from blk_mq_free_request(). > > 320 320 kworker/29:1H __blk_mq_free_request rq_flags 0x220c0 in-flight 1 RQF_MQ_INFLIGHT/RQF_DONTPREP/RQF_IO_STAT/RQF_STATS is set, and it isn't a FLUSH request. > 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]' If __blk_mq_free_request() is called from timeout, that means this request has been freed by blk_mq_free_request() already, so __blk_mq_dec_active_requests should have been run. However, one case is that __blk_mq_dec_active_requests isn't called in blk_mq_end_request_batch, so maybe your driver is nvme with multiple NSs, so can you try the following patch? diff --git a/block/blk-mq.c b/block/blk-mq.c index f6dad0886a2f..9c5dd5aa289c 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1062,6 +1062,9 @@ void blk_mq_end_request_batch(struct io_comp_batch *iob) if (iob->need_ts) __blk_mq_end_request_acct(rq, now); + if (rq->rq_flags & RQF_MQ_INFLIGHT) + __blk_mq_dec_active_requests(rq->mq_hctx); + rq_qos_done(rq->q, rq); /* Thanks, Ming
