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

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Date:   Wed, 22 Aug 2018 14:47:31 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        kernel-team@....com
Subject: Re: [PATCH 1/2] workqueue: skip lockdep wq dependency in
 cancel_work_sync()

On Wed, Aug 22, 2018 at 06:02:23AM +0200, Johannes Berg wrote:
> On Wed, 2018-08-22 at 11:45 +0900, Byungchul Park wrote:
> 
> > That should've been adjusted as well when Ingo reverted Cross-release.
> 
> I can't really say.

What do you mean?

> > It would be much easier to add each pair, acquire/release, before
> > wait_for_completion() in both flush_workqueue() and flush_work() than
> > reverting the whole commit.
> 
> The commit doesn't do much more than this though.

That also has named of lockdep_map for wq/work in a better way.

> > What's lacking is only lockdep annotations for wait_for_completion().
> 
> No, I disagree. Like I said before, we need the lockdep annotations on

You seem to be confused. I was talking about wait_for_completion() in
both flush_workqueue() and flush_work(). Without
the wait_for_completion()s, nothing matters wrt what you are concerning.

> the WQ even when we don't actually create/use the completion, so we can
> catch issues even when they don't actually happen.

This is obviously true.

Byungchul

> 
> johannes