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

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Message-ID: <20170713111209.ji6w3trt45icpuf6@hirez.programming.kicks-ass.net>
Date:   Thu, 13 Jul 2017 13:12:09 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Byungchul Park <byungchul.park@....com>
Cc:     mingo@...nel.org, tglx@...utronix.de, walken@...gle.com,
        boqun.feng@...il.com, kirill@...temov.name,
        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 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.