All of lore.kernel.org
 help / color / mirror / Atom feed
From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Bart Van Assche <Bart.VanAssche@wdc.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-block@vger.kernel.org,
	Johannes Thumshirn <jthumshirn@suse.de>,
	Alan Jenkins <alan.christopher.jenkins@gmail.com>,
	syzbot <syzbot+c4f9cebf9d651f6e54de@syzkaller.appspotmail.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Jens Axboe <axboe@kernel.dk>,
	Dan Williams <dan.j.williams@intel.com>,
	Christoph Hellwig <hch@lst.de>,
	oleksandr@natalenko.name, ming.lei@redhat.com,
	martin@lichtvoll.de, Hannes Reinecke <hare@suse.com>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	Ross Zwisler <ross.zwisler@linux.intel.com>,
	keith.busch@intel.com, linux-ext4@vger.kernel.org
Subject: Re: INFO: task hung in blk_queue_enter
Date: Mon, 4 Jun 2018 22:13:23 +0900	[thread overview]
Message-ID: <09a33861-2ddc-1a13-19f6-2a1998ca3ec5@i-love.sakura.ne.jp> (raw)
In-Reply-To: <CACT4Y+bd8oc3Y5o+mxwktefGc07aU8N25doQRDvD8g8v3TyaZw@mail.gmail.com>

On 2018/06/04 20:46, Dmitry Vyukov wrote:
> On Fri, Jun 1, 2018 at 12:10 PM, Tetsuo Handa
> <penguin-kernel@i-love.sakura.ne.jp> wrote:
>> Tetsuo Handa wrote:
>>> 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. That is, for some reason, someone who is responsible for calling
>>> percpu_ref_put(&q->q_usage_counter) (presumably via blk_queue_exit()) is
>>> unable to call percpu_ref_put().
>>> But I don't know how to find someone who is failing to call percpu_ref_put()...
>>
>> I found the someone. It was already there in the backtrace...
> 
> Nice!
> 
> Do I understand it correctly that this bug is probably the root cause
> of a whole lot of syzbot "task hung" reports? E.g. this one too?
> https://syzkaller.appspot.com/bug?id=cdc4add60bb95a4da3fec27c5fe6d75196b7f976
> I guess we will need to sweep close everything related to
> filesystems/block devices when this is committed?
> 

I can't tell it. We still have lockdep warning for loop module. Also, I suspect
that hung tasks waiting for page bit might be related to binder module.

Since we are about to merge "kernel/hung_task.c: show all hung tasks before panic"
patch, we might be able to get more hints after 4.18-rc1.

  reply	other threads:[~2018-06-04 13:13 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-28 11:24 INFO: task hung in blk_queue_enter syzbot
2018-05-15 11:45 ` Tetsuo Handa
2018-05-16 13:05   ` Tetsuo Handa
2018-05-16 14:56     ` Bart Van Assche
2018-05-16 14:56       ` Bart Van Assche
2018-05-16 15:16       ` Dmitry Vyukov
2018-05-16 15:16         ` Dmitry Vyukov
2018-05-16 15:37         ` Bart Van Assche
2018-05-16 15:37           ` Bart Van Assche
2018-05-16 15:37           ` Bart Van Assche
2018-05-21 21:52           ` Tetsuo Handa
2018-05-22 11:20             ` Tetsuo Handa
2018-06-01 10:10               ` Tetsuo Handa
2018-06-01 17:52                 ` Jens Axboe
2018-06-01 23:49                   ` Ming Lei
2018-06-02  0:49                     ` Jens Axboe
2018-06-02  0:56                       ` Jens Axboe
2018-06-02  2:36                       ` Ming Lei
2018-06-02  4:31                         ` Jens Axboe
2018-06-02  4:54                           ` Ming Lei
2018-06-02  8:07                             ` Martin Steigerwald
2018-06-02  8:07                               ` Martin Steigerwald
2018-06-02 13:48                             ` Jens Axboe
2018-06-02 13:48                               ` Jens Axboe
2018-06-05  0:27                   ` Tetsuo Handa
2018-06-05  0:41                     ` Ming Lei
2018-06-07  3:29                       ` Ming Lei
2018-06-07  3:29                         ` Ming Lei
2018-06-07 13:19                         ` Tetsuo Handa
2018-06-04 11:46                 ` Dmitry Vyukov
2018-06-04 13:13                   ` Tetsuo Handa [this message]
2018-05-16 17:33     ` Alan Jenkins

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=09a33861-2ddc-1a13-19f6-2a1998ca3ec5@i-love.sakura.ne.jp \
    --to=penguin-kernel@i-love.sakura.ne.jp \
    --cc=Bart.VanAssche@wdc.com \
    --cc=alan.christopher.jenkins@gmail.com \
    --cc=axboe@kernel.dk \
    --cc=dan.j.williams@intel.com \
    --cc=dvyukov@google.com \
    --cc=hare@suse.com \
    --cc=hch@lst.de \
    --cc=jthumshirn@suse.de \
    --cc=keith.busch@intel.com \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-ext4@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=martin.petersen@oracle.com \
    --cc=martin@lichtvoll.de \
    --cc=ming.lei@redhat.com \
    --cc=oleksandr@natalenko.name \
    --cc=ross.zwisler@linux.intel.com \
    --cc=syzbot+c4f9cebf9d651f6e54de@syzkaller.appspotmail.com \
    --cc=syzkaller-bugs@googlegroups.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.