linux-kernel - Re: [PATCH 1/2] workqueue: skip lockdep wq dependency in cancel_work

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Message-ID: <20180821172711.GR3978217@devbig004.ftw2.facebook.com>
Date:   Tue, 21 Aug 2018 10:27:11 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org
Subject: Re: [PATCH 1/2] workqueue: skip lockdep wq dependency in
 cancel_work_sync()

Hello, Johannes.

On Tue, Aug 21, 2018 at 07:18:14PM +0200, Johannes Berg wrote:
> > But this can lead to a deadlock.  I'd much rather err on the side of
> > discouraging complex lock dancing around ordered workqueues, no?
> 
> What can lead to a deadlock?

Oh not this particular case, but I was wondering whether we'd be
missing legitimate possible deadlock cases by skipping lockdep for all
cancel_work_sync()'s as they can actually flush.

Thanks.

-- 
tejun