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 S935374AbcHaOlr (ORCPT <rfc822;w@1wt.eu>);
        Wed, 31 Aug 2016 10:41:47 -0400
Received: from foss.arm.com ([217.140.101.70]:34258 "EHLO foss.arm.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S934324AbcHaOlp (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 31 Aug 2016 10:41:45 -0400
Date: Wed, 31 Aug 2016 15:41:28 +0100
From: Will Deacon <will.deacon@arm.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Yabin Cui <yabinc@google.com>, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm/perf: Fix pmu percpu irq handling at hotplug.
Message-ID: <20160831144128.GE29505@arm.com>
References: <CALJ9ZPMixfGKspzaz+vTGQZG4EaQB5Futss-aC-Z+8oztVX9Nw@mail.gmail.com>
 <20160819142514.GB28422@leverpostej>
 <20160826094800.GD13554@arm.com>
 <20160830173224.GN1223@leverpostej>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20160830173224.GN1223@leverpostej>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Aug 30, 2016 at 06:32:25PM +0100, Mark Rutland wrote:
> On Fri, Aug 26, 2016 at 10:48:00AM +0100, Will Deacon wrote:
> > On Fri, Aug 19, 2016 at 03:25:14PM +0100, Mark Rutland wrote:
> > > On Thu, Aug 18, 2016 at 01:24:38PM -0700, Yabin Cui wrote:
> > > >    If the cpu pmu is using a percpu irq:                                    
> > > >          
> > > >    1. When a cpu is down, we should disable pmu irq on                      
> > > >    that cpu. Otherwise, if the cpu is still down when                        
> > > >    the last perf event is released, the pmu irq can't                        
> > > >    be freed. Because the irq is still enabled on the                        
> > > >    offlined cpu. And following perf_event_open()                            
> > > >    syscalls will fail.                                                      
> > > >
> > > >    2. When a cpu is up, we should enable pmu irq on                          
> > > >    that cpu. Otherwise, profiling tools can't sample                        
> > > >    events on the cpu before all perf events are                              
> > > >    released, because pmu irq is disabled on that cpu.                        
> 
> [...]
> 
> > > Rather than adding more moving parts to the IRQ manipulation logic, I'd
> > > rather we rework the IRQ manipulation logic to:
> > > 
> > > * At probe time, request all the interrupts. If we can't, bail out and
> > >   fail the probe.
> > > 
> > > * Upon hotplug in (and at probe time), configure the affinity and
> > >   enable the relevant interrupt(s).
> > > 
> > > * Upon hotplug out, disable the relevant interrupt.
> 
> > > I'm taking a look at doing the above, but I don't yet have a patch.
> > 
> > Any update on this? I'd quite like to do *something* to fix the issues
> > reported here.
> 
> Apologies for the delay.
> 
> I've been away from my development hardware for the last week, so I
> ahven't fought with this for a few days.
> 
> Given it's requiring that I practically rewrite of_pmu_irq_cfg and
> friends, it may be better to take Yabin's patch for the timebeing if you
> want a quick fix for this particular issue.

Right, but that patch is totally mangled :/

I guess this will have to wait until somebody has time to rework the IRQ
code.

Will