linux-kernel - RE: [PATCH 4/4] lockdep: Fix workqueue crossrelease annotation

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Date:   Wed, 30 Aug 2017 18:24:39 +0900
From:   "Byungchul Park" <byungchul.park@....com>
To:     "'Peter Zijlstra'" <peterz@...radead.org>
Cc:     <mingo@...nel.org>, <tj@...nel.org>, <boqun.feng@...il.com>,
        <david@...morbit.com>, <johannes@...solutions.net>,
        <oleg@...hat.com>, <linux-kernel@...r.kernel.org>,
        <kernel-team@....com>
Subject: RE: [PATCH 4/4] lockdep: Fix workqueue crossrelease annotation

> -----Original Message-----
> From: Peter Zijlstra [mailto:peterz@...radead.org]
> Sent: Wednesday, August 30, 2017 6:12 PM
> To: Byungchul Park
> Cc: mingo@...nel.org; tj@...nel.org; boqun.feng@...il.com;
> david@...morbit.com; johannes@...solutions.net; oleg@...hat.com; linux-
> kernel@...r.kernel.org; kernel-team@....com
> Subject: Re: [PATCH 4/4] lockdep: Fix workqueue crossrelease annotation
> 
> On Wed, Aug 30, 2017 at 06:01:59PM +0900, Byungchul Park wrote:
> > My point is that we inevitably lose valuable dependencies by yours.
> That's
> > why I've endlessly asked you 'do you have any reason you try those
> patches?'
> > a ton of times. And you have never answered it.
> 
> The only dependencies that are lost are those between the first work and
> the setup of the workqueue thread.
> 
> And there obviously _should_ not be any dependencies between those. A

100% right. Since there obviously should not be any, it would be better
to check them. So I've endlessly asked you 'do you have any reason removing
the opportunity for that check?'. Overhead? Logical problem? Or want to
believe workqueue setup code perfect forever? I mean, is it a problem if we
check them?

> work should not depend on the setup of the thread.

100% right.