Re: INFO: task hung in blk_queue_enter

I checked counter values using debug printk() patch shown below, and found that q->q_usage_counter.count == 1 when this deadlock occurs. Since sum of percpu_count did not change after percpu_ref_kill(), this is not a race condition while folding percpu counter values into atomic counter value.

Re: INFO: task hung in blk_queue_enter

Bart Van Assche wrote: > On Wed, 2018-05-16 at 17:16 +0200, Dmitry Vyukov wrote: > > On Wed, May 16, 2018 at 4:56 PM, Bart Van Assche > > wrote: > > > On Wed, 2018-05-16 at 22:05 +0900, Tetsuo Handa wrote: > > > > diff --git a/block/blk-core.c b/block/blk-core.c > > > >

Re: INFO: task hung in blk_queue_enter

> jbd2/sda1-8(PID=2271) is stuck waiting for journal commit operation. > I don't know how this thread is involved to this problem. It feels like it should be a necessary link in the chain. This is the filesystem underneath the loop device. If that hangs, we would expect the loop device to

Re: INFO: task hung in blk_queue_enter

On Wed, 2018-05-16 at 17:16 +0200, Dmitry Vyukov wrote: > On Wed, May 16, 2018 at 4:56 PM, Bart Van Assche > wrote: > > On Wed, 2018-05-16 at 22:05 +0900, Tetsuo Handa wrote: > > > diff --git a/block/blk-core.c b/block/blk-core.c > > > index 85909b4..59e2496 100644 > > >

Re: INFO: task hung in blk_queue_enter

On Wed, May 16, 2018 at 4:56 PM, Bart Van Assche wrote: > On Wed, 2018-05-16 at 22:05 +0900, Tetsuo Handa wrote: >> One ore more threads are waiting for q->mq_freeze_depth to become 0. But the >> thread who incremented q->mq_freeze_depth at blk_freeze_queue_start(q) from

Re: INFO: task hung in blk_queue_enter

On Wed, 2018-05-16 at 22:05 +0900, Tetsuo Handa wrote: > One ore more threads are waiting for q->mq_freeze_depth to become 0. But the > thread who incremented q->mq_freeze_depth at blk_freeze_queue_start(q) from > blk_freeze_queue() is waiting at blk_mq_freeze_queue_wait(). Therefore, >

Re: INFO: task hung in blk_queue_enter

Tetsuo Handa wrote: > I couldn't check whether freeze_depth in blk_freeze_queue_start() was 1, > but presumably q->mq_freeze_depth > 0 because syz-executor7(PID=5010) is > stuck at wait_event() in blk_queue_enter(). > > Since flags == 0, preempt == false. Since stuck at wait_event(), success ==

Re: INFO: task hung in blk_queue_enter

I managed to obtain SysRq-t when khungtaskd fires using debug printk() ( https://groups.google.com/forum/#!topic/syzkaller-bugs/OTuOsVebAiE ). Only 4 threads shown below seems to be relevant to this problem. [ 246.929688] taskPC stack pid father [ 249.888937]

INFO: task hung in blk_queue_enter

Hello, syzbot hit the following crash on upstream commit d8a332730e757129e70675679f2b2a03f1ecf65e (Fri Apr 27 17:39:38 2018 +) Merge tag 'char-misc-4.17-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc syzbot dashboard link: