linux-kernel - Re: [PATCH v3] workqueue: don't skip lockdep work dependency in cancel_work

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Date:   Mon, 15 Aug 2022 11:16:00 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Johannes Berg <johannes.berg@...el.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Hillf Danton <hdanton@...a.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] workqueue: don't skip lockdep work dependency in
 cancel_work_sync()

On Fri, Jul 29, 2022 at 01:30:23PM +0900, Tetsuo Handa wrote:
> Like Hillf Danton mentioned
> 
>   syzbot should have been able to catch cancel_work_sync() in work context
>   by checking lockdep_map in __flush_work() for both flush and cancel.
> 
> in [1], being unable to report an obvious deadlock scenario shown below is
> broken. From locking dependency perspective, sync version of cancel request
> should behave as if flush request, for it waits for completion of work if
> that work has already started execution.

Applied to cgroup/for-6.0-fixes.

Thanks.

-- 
tejun