LKML Archive on 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 13:14 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-28 11:24 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 15:16       ` Dmitry Vyukov
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 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 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 \
    --subject='Re: INFO: task hung in blk_queue_enter' \
    /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

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).