linux-kernel - Re: [PATCH 20/28] locking/lockdep: Refactorize check_noncircular and check

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Date:   Fri, 26 Apr 2019 14:48:37 +0800
From:   Yuyang Du <duyuyang@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     will.deacon@....com, Ingo Molnar <mingo@...nel.org>,
        Bart Van Assche <bvanassche@....org>, ming.lei@...hat.com,
        Frederic Weisbecker <frederic@...nel.org>, tglx@...utronix.de,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 20/28] locking/lockdep: Refactorize check_noncircular and check_redundant

Thanks for review.

On Fri, 26 Apr 2019 at 03:48, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Wed, Apr 24, 2019 at 06:19:26PM +0800, Yuyang Du wrote:
> > These two functions now handle different check results themselves. A new
> > check_path function is added to check whether there is a path in the
> > dependency graph. No functional change.
>
> This looks good, however I completely forgot we still had the redundant
> thing.
>
> It was added for cross-release (which has since been reverted) which
> would generate a lot of redundant links (IIRC) but having it makes the
> reports more convoluted -- basically, if we had an A-B-C relation, then
> A-C will not be added to the graph because it is already covered. This
> then means any report will include B, even though a shorter cycle might
> have been possible.
>
> Maybe we should make the whole redundant check depend on LOCKDEP_SMALL
> for now.

Sure. I can do that.