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

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Message-ID: <CANrsvRMZ=i+L1sQzPiMVzpTOduNnTw_gKqcNkBVWPdpDs5fQZA@mail.gmail.com>
Date:   Thu, 13 Jul 2017 20:23:33 +0900
From:   Byungchul Park <max.byungchul.park@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Byungchul Park <byungchul.park@....com>,
        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 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.

So it works.


-- 
Thanks,
Byungchul