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 S1751805AbcGOQRJ (ORCPT <rfc822;w@1wt.eu>);
	Fri, 15 Jul 2016 12:17:09 -0400
Received: from foss.arm.com ([217.140.101.70]:50234 "EHLO foss.arm.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751743AbcGOQRI (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Fri, 15 Jul 2016 12:17:08 -0400
Date: Fri, 15 Jul 2016 17:16:54 +0100
From: Mark Rutland <mark.rutland@arm.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, rt@linutronix.de,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Will Deacon <will.deacon@arm.com>
Subject: Re: [patch V2 35/67] arm/perf: Convert to hotplug state machine
Message-ID: <20160715161654.GF19840@leverpostej>
References: <20160713153219.128052238@linutronix.de>
 <20160713153335.794097159@linutronix.de>
 <20160715130818.GA19840@leverpostej>
 <20160715152629.GB16938@linutronix.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20160715152629.GB16938@linutronix.de>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, Jul 15, 2016 at 05:26:30PM +0200, Sebastian Andrzej Siewior wrote:
> * Mark Rutland | 2016-07-15 14:08:18 [+0100]:
> 
> >Hi,
> Hi Mark,
> 
> >We may have multiple PMUs (e.g. two in big.LITTLE systems), and
> >__oprofile_cpu_pmu only contains one of these. So this conversion is not
> >correct.
> >
> >We were relying on the notifier list implicitly containing a list of
> >those PMUs. It seems like we need an explicit list here.
> >
> >We keep __oprofile_cpu_pmu around for legacy 32-bit users of OProfile
> >(on non-hetereogeneous systems), and that's all that the variable should
> >be used for.
> 
> By the time I'e been looking there was only one node in the .dts. Now
> you say it is not only possible but likely to have more than one node.

Yes. For example, arch/arm/boot/dts/vexpress-v2p-ca15_a7.dts is a
big.LITTLE system with a Cortex-A7 PMU and a Cortex-A15 PMU.

> So what we need is a list which gets extended in cpu_pmu_init() instead
> of using the global pointer we have now. Correct?

Yes, that sounds right to me, with matching removal in cpu_pmu_destroy.

Thanks,
Mark.