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 S1754185AbbEZNWd (ORCPT <rfc822;w@1wt.eu>);
	Tue, 26 May 2015 09:22:33 -0400
Received: from bombadil.infradead.org ([198.137.202.9]:37975 "EHLO
	bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753537AbbEZNW2 (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 26 May 2015 09:22:28 -0400
Date: Tue, 26 May 2015 15:22:21 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: Ingo Molnar <mingo@kernel.org>, Vince Weaver <vincent.weaver@maine.edu>,
        Jiri Olsa <jolsa@redhat.com>, "Liang, Kan" <kan.liang@intel.com>,
        LKML <linux-kernel@vger.kernel.org>, Andrew Hunter <ahh@google.com>,
        Maria Dimakopoulou <maria.n.dimakopoulou@gmail.com>
Subject: Re: [PATCH v2 01/11] perf,x86: Fix event/group validation
Message-ID: <20150526132221.GP3644@twins.programming.kicks-ass.net>
References: <20150522132905.416122812@infradead.org>
 <20150522133135.353044581@infradead.org>
 <20150522134056.GG3644@twins.programming.kicks-ass.net>
 <CABPqkBTzQ0z6erv4dnotFKu=KystkSRJG2ovxBhsp5vFFFufqg@mail.gmail.com>
 <20150526101237.GK3644@twins.programming.kicks-ass.net>
 <CABPqkBQcKLoHCS3=_1cj4-JCTiOzWDc1=vGp85T-nnoAJQd5-Q@mail.gmail.com>
 <20150526121619.GN3644@twins.programming.kicks-ass.net>
 <CABPqkBQbw=vx+hFX+gAFQRkHpkpzz6meucpdo4eMfQ6Xu_XzvA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CABPqkBQbw=vx+hFX+gAFQRkHpkpzz6meucpdo4eMfQ6Xu_XzvA@mail.gmail.com>
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 Tue, May 26, 2015 at 05:25:59AM -0700, Stephane Eranian wrote:
> > IIRC the problem was that the copy from c2 into c1:
> >
> >         if (c1 && (c1->flags & PERF_X86_EVENT_DYNAMIC)) {
> >                 bitmap_copy(c1->idxmsk, c2->idxmsk, X86_PMC_IDX_MAX);
> >                 c1->weight = c2->weight;
> >                 c2 = c1;
> >         }
> >
> > is incomplete. For instance, flags is not copied, and some code down the
> > line might check that and get wrong flags.
> >
> Ok, now I remember this code. It has to do with incremental scheduling.
> Suppose E1, E2, E3 events where E1 is exclusive. The first call is
> for scheduling E1. It gets to get_event_constraint() which "allocates" a
> dynamic constraint. The second call  tries to schedule E1, E2. But the
> second time for E1, you already have the dynamic constraint allocated, so
> this code is reusing the constraint storage and just updates the bitmask
> and weight.
> 
> Now, that the storage is not actually dynamic (kmalloc'd), but taken from a
> fixed size array in cpuc, I believe we can simplify this and "re-allocate"
> the constraint for each incremental call to intel_get_event_constraints().
> Do you agree?

That would probably work, the whole incremental thing seems superfluous
to me.