From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1030628AbbKDPgz (ORCPT <rfc822;w@1wt.eu>);
	Wed, 4 Nov 2015 10:36:55 -0500
Received: from casper.infradead.org ([85.118.1.10]:53229 "EHLO
	casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S932491AbbKDPgx (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 4 Nov 2015 10:36:53 -0500
Date: Wed, 4 Nov 2015 16:36:51 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dave Jones <davej@codemonkey.org.uk>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>, Stephane Eranian <eranian@gmail.com>,
        Andi Kleen <andi@firstfloor.org>
Subject: Re: perf related lockdep bug
Message-ID: <20151104153651.GC11639@twins.programming.kicks-ass.net>
References: <20151104051717.GA6098@codemonkey.org.uk>
 <20151104102151.GG17308@twins.programming.kicks-ass.net>
 <20151104102800.GZ11639@twins.programming.kicks-ass.net>
 <20151104105010.GA11639@twins.programming.kicks-ass.net>
 <20151104134838.GR29027@linux.vnet.ibm.com>
 <20151104142058.GX3604@twins.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20151104142058.GX3604@twins.programming.kicks-ass.net>
User-Agent: Mutt/1.5.21 (2012-12-30)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, Nov 04, 2015 at 03:20:58PM +0100, Peter Zijlstra wrote:
> On Wed, Nov 04, 2015 at 05:48:38AM -0800, Paul E. McKenney wrote:
> > This problem is caused by the IPI handler interrupting the RCU read-side
> > critical section.  One way to prevent the IPI from doing this is to
> > disable interrupts across the RCU read-side critical section instead
> > of merely disabling preemption.  This is a reasonable approach given
> > that acquiring the scheduler locks is going to disable interrupts
> > in any case.
> > 
> > The (untested) patch below takes this approach.
> > 
> > Thoughts?
> 
> Yes, this should work, but now I worry I need to go audit all of perf
> and sched for this :/

I can't find any other sites just now, so let me queue this.

I also had a brief look if you used any other locks under rnp->lock, but
aside from the printk and sched things it seems clean.