Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751568AbdGMLM2 (ORCPT <rfc822;w@1wt.eu>);
        Thu, 13 Jul 2017 07:12:28 -0400
Received: from merlin.infradead.org ([205.233.59.134]:43450 "EHLO
        merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751079AbdGMLM0 (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 13 Jul 2017 07:12:26 -0400
Date: Thu, 13 Jul 2017 13:12:09 +0200
From: Peter Zijlstra <peterz@infradead.org>
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
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>
 <20170711161232.GB28975@worktop>
 <20170712020053.GB20323@X58A-UD3R>
 <20170712075617.o2jds2giuoqxjqic@hirez.programming.kicks-ass.net>
 <20170713020745.GG20323@X58A-UD3R>
 <20170713081442.GA439@worktop>
 <20170713085746.GH20323@X58A-UD3R>
 <20170713095052.dssev34f7c43vlok@hirez.programming.kicks-ass.net>
 <20170713100953.GI20323@X58A-UD3R>
 <20170713102905.ysrvn7td6ryt4jaj@hirez.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20170713102905.ysrvn7td6ryt4jaj@hirez.programming.kicks-ass.net>
User-Agent: NeoMutt/20170609 (1.8.3)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 709
Lines: 32

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.