linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: bot+e38be687a2450270a3b593bacb6b5795a7a74edb@syzkaller.appspotmail.com,
	syzkaller-bugs@googlegroups.com
Cc: dvyukov@google.com, gregkh@linuxfoundation.org,
	kstewart@linuxfoundation.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, pombredanne@nexb.com, tglx@linutronix.de
Subject: Re: BUG: workqueue lockup (2)
Date: Tue, 19 Dec 2017 23:27:24 +0900	[thread overview]
Message-ID: <201712192327.FIJ64026.tMQFOOVFFLHOSJ@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <001a113f711a528a3f0560b08e76@google.com>

syzbot wrote:
> 
> syzkaller has found reproducer for the following crash on  
> f3b5ad89de16f5d42e8ad36fbdf85f705c1ae051

"BUG: workqueue lockup" is not a crash.

> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
> 
> 
> BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 37s!
> BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=-20 stuck for 32s!
> Showing busy workqueues and worker pools:
> workqueue events: flags=0x0
>    pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
>      pending: cache_reap
> workqueue events_power_efficient: flags=0x80
>    pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256
>      pending: neigh_periodic_work, do_cache_clean
> workqueue mm_percpu_wq: flags=0x8
>    pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
>      pending: vmstat_update
> workqueue kblockd: flags=0x18
>    pwq 3: cpus=1 node=0 flags=0x0 nice=-20 active=1/256
>      pending: blk_timeout_work

You gave up too early. There is no hint for understanding what was going on.
While we can observe "BUG: workqueue lockup" under memory pressure, there is
no hint like SysRq-t and SysRq-m. Thus, I can't tell something is wrong.

At least you need to confirm that lockup lasts for a few minutes. Otherwise,
this might be just overstressing. (According to repro.c , 12 threads are
created and soon SEGV follows? According to above message, only 2 CPUs?
Triggering SEGV suggests memory was low due to saving coredump?)

  reply	other threads:[~2017-12-19 14:27 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <94eb2c03c9bc75aff2055f70734c@google.com>
2017-12-03 14:36 ` BUG: workqueue lockup (2) Dmitry Vyukov
2017-12-03 14:48   ` Thomas Gleixner
2017-12-04 11:08     ` Tetsuo Handa
2017-12-19 12:25 ` syzbot
2017-12-19 14:27   ` Tetsuo Handa [this message]
2017-12-19 14:40     ` Dmitry Vyukov
2017-12-19 16:37       ` Dmitry Vyukov
2017-12-20 10:55         ` Tetsuo Handa
2017-12-21 10:19           ` Dmitry Vyukov
2017-12-21 10:22           ` Dmitry Vyukov
2017-12-21 11:04           ` Dmitry Vyukov
2017-12-21 13:07             ` Tetsuo Handa
2017-12-28 13:43               ` Dmitry Vyukov
2018-05-12 21:52   ` Eric Biggers
2018-05-13  2:06     ` Tetsuo Handa
2018-05-13  3:32       ` Eric Biggers
2018-05-13 14:29         ` Tetsuo Handa
2018-05-13 14:35           ` Dmitry Vyukov

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=201712192327.FIJ64026.tMQFOOVFFLHOSJ@I-love.SAKURA.ne.jp \
    --to=penguin-kernel@i-love.sakura.ne.jp \
    --cc=bot+e38be687a2450270a3b593bacb6b5795a7a74edb@syzkaller.appspotmail.com \
    --cc=dvyukov@google.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=kstewart@linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=pombredanne@nexb.com \
    --cc=syzkaller-bugs@googlegroups.com \
    --cc=tglx@linutronix.de \
    /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 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).