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

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Message-ID: <20170907001155.GD3240@X58A-UD3R>
Date:   Thu, 7 Sep 2017 09:11:55 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Boqun Feng <boqun.feng@...il.com>, peterz@...radead.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Byungchul Park <max.byungchul.park@...il.com>,
        Ingo Molnar <mingo@...nel.org>, Tejun Heo <tj@...nel.org>,
        david@...morbit.com, Johannes Berg <johannes@...solutions.net>,
        oleg@...hat.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kernel-team@....com
Subject: Re: [PATCH 4/4] lockdep: Fix workqueue crossrelease annotation

On Wed, Sep 06, 2017 at 10:32:54AM +0900, Byungchul Park wrote:
> > What do you mean by "false dependencies"? AFAICT, recursive-read could
> 
> All locks used in every work->func() generate false dependencies with
> 'work' and 'wq', while any flush works are not involved. It's inevitable.
> 
> Moreover, it's also possible to generate more false ones between the
> pseudo acquisitions, if real acquisitions are used for that speculative
> purpose e.i. recursive-read here, which are anyway real ones.
> 
> Moreover, it's also possible to generate more false ones between holding
> locks and the pseudo ones, of course, the workqueue code is not the case
> for now.
> 
> Moreover, it's also possible to generate more false ones between the
> pseudo ones and crosslocks on commit, once making crossrelease work even
> for recursive-read things.

Hi Peter,

What do you think about the above? Just let me know please. It's ok if
you think it's not needed yet.

Or, if you think it's necessary from now on, I'm going ahead for that
work, starting from renaming the 'might' thing.