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From: Byungchul Park <max.byungchul.park@gmail.com>
Date: Thu, 13 Jul 2017 20:23:33 +0900
Message-ID: <CANrsvRMZ=i+L1sQzPiMVzpTOduNnTw_gKqcNkBVWPdpDs5fQZA@mail.gmail.com>
Subject: Re: [PATCH v7 06/16] lockdep: Detect and handle hist_lock ring buffer overwrite
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To: Peter Zijlstra <peterz@infradead.org>
Cc: Byungchul Park <byungchul.park@lge.com>, Ingo Molnar <mingo@kernel.org>, tglx@linutronix.de, Michel Lespinasse <walken@google.com>, boqun.feng@gmail.com, kirill@shutemov.name, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, linux-mm@kvack.org, akpm@linux-foundation.org, willy@infradead.org, npiggin@gmail.com, kernel-team@lge.com

On Thu, Jul 13, 2017 at 8:12 PM, Peter Zijlstra <peterz@infradead.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

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