linux-kernel - Re: [PATCH v7 06/16] lockdep: Detect and handle hist

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Message-ID: <20170714014127.GJ20323@X58A-UD3R>
Date:   Fri, 14 Jul 2017 10:41:27 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Byungchul Park <max.byungchul.park@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, tglx@...utronix.de,
        Michel Lespinasse <walken@...gle.com>, boqun.feng@...il.com,
        kirill@...temov.name,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-mm@...ck.org, akpm@...ux-foundation.org, willy@...radead.org,
        npiggin@...il.com, kernel-team@....com
Subject: Re: [PATCH v7 06/16] lockdep: Detect and handle hist_lock ring
 buffer overwrite

On Thu, Jul 13, 2017 at 08:23:33PM +0900, Byungchul Park wrote:
> On Thu, Jul 13, 2017 at 8:12 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Thu, Jul 13, 2017 at 12:29:05PM +0200, Peter Zijlstra wrote:
> >> On Thu, Jul 13, 2017 at 07:09:53PM +0900, Byungchul Park wrote:
> >> > On Thu, Jul 13, 2017 at 11:50:52AM +0200, Peter Zijlstra wrote:
> >> > >   wait_for_completion(&C);
> >> > >     atomic_inc_return();
> >> > >
> >> > >                                   mutex_lock(A1);
> >> > >                                   mutex_unlock(A1);
> >> > >
> >> > >
> >> > >                                   <IRQ>
> >> > >                                     spin_lock(B1);
> >> > >                                     spin_unlock(B1);
> >> > >
> >> > >                                     ...
> >> > >
> >> > >                                     spin_lock(B64);
> >> > >                                     spin_unlock(B64);
> >> > >                                   </IRQ>
> >> > >
> >> > >
> >
> > Also consider the alternative:
> >
> >                                         <IRQ>
> >                                           spin_lock(D);
> >                                           spin_unlock(D);
> >
> >                                           complete(&C);
> >                                         </IRQ>
> >
> > in which case the context test will also not work.
> 
> Context tests are done on xhlock with the release context, _not_
> acquisition context. For example, spin_lock(D) and complete(&C) are
> in the same context, so the test would pass in this example.

Something wrong?