linux-kernel - Re: general protection fault in wb

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Message-ID: <1a40d046-9994-ad02-8f29-c4952429e557@I-love.SAKURA.ne.jp>
Date:   Tue, 24 Apr 2018 06:43:00 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Tejun Heo <tj@...nel.org>, Jan Kara <jack@...e.cz>,
        Jens Axboe <axboe@...com>, linux-block@...r.kernel.org
Cc:     syzbot <syzbot+9873874c735f2892e7e9@...kaller.appspotmail.com>,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk
Subject: Re: general protection fault in wb_workfn

On 2018/04/23 19:09, Tetsuo Handa wrote:
> By the way, I got a newbie question regarding commit 5318ce7d46866e1d ("bdi:
> Shutdown writeback on all cgwbs in cgwb_bdi_destroy()"). It uses clear_bit()
> to clear WB_shutting_down bit so that threads waiting at wait_on_bit() will
> wake up. But clear_bit() itself does not wake up threads, does it? Who wakes
> them up (e.g. by calling wake_up_bit()) after clear_bit() was called?
> 

Below report might be waiting for wake_up_bit() ?

  INFO: task hung in wb_shutdown (2)
  https://syzkaller.appspot.com/bug?id=b297474817af98d5796bc544e1bb806fc3da0e5e