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Date: Thu, 13 Jul 2017 13:12:09 +0200
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v7 06/16] lockdep: Detect and handle hist_lock ring
 buffer overwrite
Message-ID: <20170713111209.ji6w3trt45icpuf6@hirez.programming.kicks-ass.net>
References: <1495616389-29772-7-git-send-email-byungchul.park@lge.com>
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Sender: owner-linux-mm@kvack.org
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To: Byungchul Park <byungchul.park@lge.com>
Cc: mingo@kernel.org, tglx@linutronix.de, walken@google.com, boqun.feng@gmail.com, kirill@shutemov.name, 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 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.

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