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

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Message-ID: <20170906235933.GC3240@X58A-UD3R>
Date:   Thu, 7 Sep 2017 08:59:33 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Boqun Feng <boqun.feng@...il.com>
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:
> 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.

Of course, this problem can be ignored if we *only* use recursive-read
acquisitions for the speculative purpose, though current workqueue
code uses both recursive-read and normal(write) for that.

IOW, as long as we leave the write acquisions for that purpose, this
would still be a problem.