linux-kernel - Re: INFO: task hung in wb

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Date:   Thu, 3 May 2018 09:25:13 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        torvalds@...ux-foundation.org
Cc:     jack@...e.cz, tj@...nel.org,
        syzbot+c0cf869505e03bdf1a24@...kaller.appspotmail.com,
        christophe.jaillet@...adoo.fr, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, syzkaller-bugs@...glegroups.com,
        zhangweiping@...ichuxing.com, akpm@...ux-foundation.org,
        dvyukov@...gle.com, linux-block@...r.kernel.org
Subject: Re: INFO: task hung in wb_shutdown (2)

On 5/1/18 4:14 PM, Tetsuo Handa wrote:
>>>From 1b90d7f71d60e743c69cdff3ba41edd1f9f86f93 Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Date: Wed, 2 May 2018 07:07:55 +0900
> Subject: [PATCH v2] bdi: wake up concurrent wb_shutdown() callers.
> 
> syzbot is reporting hung tasks at wait_on_bit(WB_shutting_down) in
> wb_shutdown() [1]. This seems to be because commit 5318ce7d46866e1d ("bdi:
> Shutdown writeback on all cgwbs in cgwb_bdi_destroy()") forgot to call
> wake_up_bit(WB_shutting_down) after clear_bit(WB_shutting_down).
> 
> Introduce a helper function clear_and_wake_up_bit() and use it, in order
> to avoid similar errors in future.

Queued up, thanks Tetsuo!

-- 
Jens Axboe