Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755564AbbDIO1L (ORCPT ); Thu, 9 Apr 2015 10:27:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53814 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755532AbbDIO1H (ORCPT ); Thu, 9 Apr 2015 10:27:07 -0400 Message-ID: <1428589600.20354.27.camel@deneb.redhat.com> Subject: Re: [PATCH] drivers: CCI: fix used_mask init in validate_group() From: Mark Salter To: Mark Rutland Cc: Will Deacon , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Date: Thu, 09 Apr 2015 10:26:40 -0400 In-Reply-To: <20150409142047.GC9648@leverpostej> References: <1428517284-7951-1-git-send-email-msalter@redhat.com> <20150409135124.GA9648@leverpostej> <1428588703.20354.23.camel@deneb.redhat.com> <20150409142047.GC9648@leverpostej> Organization: Red Hat, Inc Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2399 Lines: 60 On Thu, 2015-04-09 at 15:20 +0100, Mark Rutland wrote: > On Thu, Apr 09, 2015 at 03:11:43PM +0100, Mark Salter wrote: > > On Thu, 2015-04-09 at 14:51 +0100, Mark Rutland wrote: > > > On Wed, Apr 08, 2015 at 07:21:24PM +0100, Mark Salter wrote: > > > > Currently in validate_group(), there is a static initializer > > > > for fake_pmu.used_mask which is based on CPU_BITS_NONE but > > > > the used_mask array size is based on CCI_PMU_MAX_HW_EVENTS. > > > > CCI_PMU_MAX_HW_EVENTS is not based on NR_CPUS, so CPU_BITS_NONE > > > > is not correct and will cause a build failure if NR_CPUS > > > > is set high enough to make CPU_BITS_NONE larger than used_mask. > > > > > > Whoops. My bad. > > > > > > > This patch changes the used_mask initialization to be runtime > > > > based on the actual size of the array. > > > > > > > > Signed-off-by: Mark Salter > > > > --- > > > > drivers/bus/arm-cci.c | 14 +++++++------- > > > > 1 file changed, 7 insertions(+), 7 deletions(-) > > > > > > > > diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c > > > > index 84fd660..1d83072 100644 > > > > --- a/drivers/bus/arm-cci.c > > > > +++ b/drivers/bus/arm-cci.c > > > > @@ -679,13 +679,13 @@ static int > > > > validate_group(struct perf_event *event) > > > > { > > > > struct perf_event *sibling, *leader = event->group_leader; > > > > - struct cci_pmu_hw_events fake_pmu = { > > > > - /* > > > > - * Initialise the fake PMU. We only need to populate the > > > > - * used_mask for the purposes of validation. > > > > - */ > > > > - .used_mask = CPU_BITS_NONE, > > > > > > Can we not simply change this to: > > > > > > .used_mask = { 0 }, > > > > > > That should result in the entire array being zeroed. > > > > It does, but it also causes the whole struct to be cleared. > > Sure, but it's also the minimal diff, and it's easier to read. This was > what the code was intended to be initially. > > > With the memset, only used_mask gets cleared. > > Is there an appreciable difference between the two performance-wise? I dunno. It is 3 strp insns vs 1 str. If you want the static init, I'll send another patch. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/