linux-kernel - Re: BUG: workqueue lockup (2)

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Message-ID: <CACT4Y+Ybe4RFYdetcKV=YyXeDc6ePSMgd0gURXzoCz6k37Jeqw@mail.gmail.com>
Date:   Thu, 21 Dec 2017 11:19:06 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     syzbot 
        <bot+e38be687a2450270a3b593bacb6b5795a7a74edb@...kaller.appspotmail.com>,
        syzkaller-bugs@...glegroups.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: BUG: workqueue lockup (2)

On Wed, Dec 20, 2017 at 11:55 AM, Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
> Dmitry Vyukov wrote:
>> On Tue, Dec 19, 2017 at 3:27 PM, Tetsuo Handa
>> <penguin-kernel@...ove.sakura.ne.jp> wrote:
>> > syzbot wrote:
>> >>
>> >> syzkaller has found reproducer for the following crash on
>> >> f3b5ad89de16f5d42e8ad36fbdf85f705c1ae051
>> >
>> > "BUG: workqueue lockup" is not a crash.
>>
>> Hi Tetsuo,
>>
>> What is the proper name for all of these collectively?
>
> I think that things which lead to kernel panic when /proc/sys/kernel/panic_on_oops
> was set to 1 are called an "oops" (or a "kerneloops").
>
> Speak of "BUG: workqueue lockup", this is not an "oops". This message was
> added by 82607adcf9cdf40f ("workqueue: implement lockup detector"), and
> this message does not always indicate a fatal problem. This message can be
> printed when the system is really out of CPU and memory. As far as I tested,
> I think that workqueue was not able to run on specific CPU due to a soft
> lockup bug.


There are also warnings which don't panic normally, unless
panic_on_warn is set. There are also cases when we suddenly lost a
machine and have no idea what happened with it. And also cases when we
are kind-a connected, and nothing bad is printed on console, but it's
still un-operable.
The only collective name I can think of is bug. We could change it to
bug. Otherwise since there are multiple names, I don't think it's
worth spending more time on this.