Date: Tue, 5 Sep 2017 17:57:27 +0900
From: Byungchul Park <byungchul.park@lge.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Byungchul Park <max.byungchul.park@gmail.com>,
        Ingo Molnar <mingo@kernel.org>, Tejun Heo <tj@kernel.org>,
        Boqun Feng <boqun.feng@gmail.com>, david@fromorbit.com,
        Johannes Berg <johannes@sipsolutions.net>, oleg@redhat.com,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        kernel-team@lge.com
Subject: Re: [PATCH 4/4] lockdep: Fix workqueue crossrelease annotation
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On Tue, Sep 05, 2017 at 09:19:30AM +0200, Peter Zijlstra wrote:
> On Tue, Sep 05, 2017 at 09:08:25AM +0200, Peter Zijlstra wrote:
> > So you worry about max_active==1 ? Or you worry about pool->lock or
> > about the thread setup? I'm still not sure.
> 
> So the thing about pool->lock is that its a leaf lock, we take nothing

I think the following sentence is a key, I hope...

Leaf locks can also create dependecies with *crosslocks*. These
dependencies are not built between holding locks like typical locks.

> inside it. Futhermore its a spinlock and therefore blocking things like
> completions or page-lock cannot form a deadlock with it.

I agree. Now we should be only interested in blocking things.

> It is also fully isolated inside workqueue.c and easy to audit.
> 
> This is why I really can't be arsed about it.
> 
> And the whole setup stuff isn't properly preserved between works in any
> case, only the first few works would ever see that history, so why
> bother.

As I said in another reply, what about (1), (3) and (5) in my example?