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Date:   Sun, 13 Feb 2022 17:33:46 +0200
From:   Leon Romanovsky <leon@kernel.org>
To:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc:     Bart Van Assche <bvanassche@acm.org>,
        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>
Subject: Re: [syzbot] possible deadlock in worker_thread
Message-ID: <Ygkk2lRe7Ndg1528@unreal>
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On Sun, Feb 13, 2022 at 02:14:09AM +0900, Tetsuo Handa wrote:
> On 2022/02/13 1:37, Bart Van Assche wrote:
> > 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.
> 

I second to Bart's request to do not deprecate system-wide workqueues.

Thanks

>