linux-kernel - Re: [PATCH 3/4] locking/ww_mutex: Treat ww_mutex

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Message-ID: <YFL1Ag8MrP6wCZjy@boqun-archlinux>
Date:   Thu, 18 Mar 2021 14:36:50 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     Waiman Long <longman@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        linux-kernel@...r.kernel.org, Juri Lelli <juri.lelli@...hat.com>
Subject: Re: [PATCH 3/4] locking/ww_mutex: Treat ww_mutex_lock() like a
 trylock

On Wed, Mar 17, 2021 at 10:54:17PM -0400, Waiman Long wrote:
> On 3/17/21 10:24 PM, Boqun Feng wrote:
> > Hi Waiman,
> > 
> > Just a question out of curiosity: how does this problem hide so long?
> > ;-) Because IIUC, both locktorture and ww_mutex_lock have been there for
> > a while, so why didn't we spot this earlier?
> > 
> > I ask just to make sure we don't introduce the problem because of some
> > subtle problems in lock(dep).
> > 
> You have to explicitly specify ww_mutex in the locktorture module parameter
> to run the test. ww_mutex is usually not the intended target of testing as
> there aren't that many places that use it. Even if someone run it, it
> probably is not on a debug kernel.
> 
> Our QA people try to run locktorture on ww_mutex and discover that.
> 

Got it. Thanks ;-)

Regards,
Boqun

> Cheers,
> Longman
>