linux-kernel - Re: [PATCH 11/12] locking/mutex: Revive fast functions for CONFIG_LOCK

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Date:   Wed, 9 Feb 2022 12:15:19 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Byungchul Park <byungchul.park@....com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Radoslaw Burny <rburny@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH 11/12] locking/mutex: Revive fast functions for CONFIG_LOCK_TRACEPOINTS

Hi Peter,

On Wed, Feb 9, 2022 at 12:41 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Tue, Feb 08, 2022 at 10:42:07AM -0800, Namhyung Kim wrote:
> > I'm not entirely sure why it removed the fast versions when lockdep is
> > on.  It seems easy to add the required annotation when the fast
> > version is succeeded as far as the tracpoints are concerned.
>
> IIRC it was something like, lockdep depends on MUTEX_DEBUG and that in
> turn relied on not having the fast path enabled. MUTEX_DEBUG used to
> always take the wait_lock to ensure the debug state is consistent with
> the lock state.

I see.  Thanks for the explanation!

Namhyung