On 5/13/23 2:54?PM, Simon Horman wrote: > 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. >> >> 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> >> --- >> block/blk-mq.c | 7 ++++--- >> 1 file changed, 4 insertions(+), 3 deletions(-) >> >> diff --git a/block/blk-mq.c b/block/blk-mq.c >> index 9c8dc70020bc..732a39d88cd6 100644 >> --- a/block/blk-mq.c >> +++ b/block/blk-mq.c >> @@ -716,6 +716,10 @@ static void __blk_mq_free_request(struct request *rq) >> blk_crypto_free_request(rq); >> blk_pm_mark_last_busy(rq); >> rq->mq_hctx = NULL; >> + >> + if (rq->rq_flags & RQF_MQ_INFLIGHT) >> + __blk_mq_dec_active_requests(hctx); >> + >> if (rq->tag != BLK_MQ_NO_TAG) >> blk_mq_put_tag(hctx->tags, ctx, rq->tag); >> if (sched_tag != BLK_MQ_NO_TAG) >> @@ -733,9 +737,6 @@ void blk_mq_free_request(struct request *rq) >> q->elevator->type->ops.finish_request) >> q->elevator->type->ops.finish_request(rq); >> >> - if (rq->rq_flags & RQF_MQ_INFLIGHT) >> - __blk_mq_dec_active_requests(hctx); >> - > > Unless I am mistaken, hctx is now unused in this function. Indeed. Tian, first one didn't compile and this one will most certainly spew a warning. That's 2 for 2 so far. I realize that you tested this one a different kernel in prod, but don't seen stuff you haven't even compiled. -- Jens Axboe
