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Subject: Re: INFO: task hung in wb_shutdown (2)
To:     Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        torvalds@linux-foundation.org
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From:   Jens Axboe <axboe@kernel.dk>
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Date:   Thu, 3 May 2018 09:25:13 -0600
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On 5/1/18 4:14 PM, Tetsuo Handa wrote:
>>From 1b90d7f71d60e743c69cdff3ba41edd1f9f86f93 Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@I-love.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