Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 18 Mar 2021 14:36:50 +0800
From:   Boqun Feng <boqun.feng@gmail.com>
To:     Waiman Long <longman@redhat.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Davidlohr Bueso <dave@stgolabs.net>,
        linux-kernel@vger.kernel.org, Juri Lelli <juri.lelli@redhat.com>
Subject: Re: [PATCH 3/4] locking/ww_mutex: Treat ww_mutex_lock() like a
 trylock
Message-ID: <YFL1Ag8MrP6wCZjy@boqun-archlinux>
References: <20210316153119.13802-1-longman@redhat.com>
 <20210316153119.13802-4-longman@redhat.com>
 <YFK5yBIOTiCdFLNm@boqun-archlinux>
 <64af1d7b-6720-0ac1-4a55-bb0acb642c6f@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <64af1d7b-6720-0ac1-4a55-bb0acb642c6f@redhat.com>
Precedence: bulk

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
>