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Date:   Sat, 12 Feb 2022 08:37:55 -0800
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Subject: Re: [syzbot] possible deadlock in worker_thread
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To:     Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        syzbot <syzbot+831661966588c802aae9@syzkaller.appspotmail.com>,
        jgg@ziepe.ca, linux-kernel@vger.kernel.org,
        linux-rdma@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        Tejun Heo <tj@kernel.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>
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 <ccd04d8a-154b-543e-e1c3-84bc655508d1@I-love.SAKURA.ne.jp>
From:   Bart Van Assche <bvanassche@acm.org>
In-Reply-To: <ccd04d8a-154b-543e-e1c3-84bc655508d1@I-love.SAKURA.ne.jp>
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On 2/11/22 21:31, Tetsuo Handa wrote:
> But this report might be suggesting us that we should consider
> deprecating (and eventually getting rid of) system-wide workqueues
> (declared in include/linux/workqueue.h), for since flush_workqueue()
> synchronously waits for completion, sharing system-wide workqueues
> among multiple modules can generate unexpected locking dependency
> chain (like this report).

I do not agree with deprecating system-wide workqueues. I think that all 
flush_workqueue(system_long_wq) calls should be reviewed since these are 
deadlock-prone.

Thanks,

Bart.