From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755119Ab1GFRlh (ORCPT ); Wed, 6 Jul 2011 13:41:37 -0400 Received: from mail-fx0-f52.google.com ([209.85.161.52]:43159 "EHLO mail-fx0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752870Ab1GFRlf (ORCPT ); Wed, 6 Jul 2011 13:41:35 -0400 Date: Wed, 6 Jul 2011 21:41:32 +0400 From: Cyrill Gorcunov To: Steven Rostedt Cc: Ingo Molnar , Peter Zijlstra , Don Zickus , Stephane Eranian , LKML Subject: Re: [PATCH -tip/perf/core] perf, x86: P4 PMU - Drop redundant WARN_ON_ONCE Message-ID: <20110706174131.GK5485@sun> References: <20110706172454.GJ5485@sun> <1309973921.26417.188.camel@gandalf.stny.rr.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1309973921.26417.188.camel@gandalf.stny.rr.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 06, 2011 at 01:38:41PM -0400, Steven Rostedt wrote: > On Wed, 2011-07-06 at 21:24 +0400, Cyrill Gorcunov wrote: > > This WARN_ON_ONCE triggers a false alarm on SMP because > > nmi-watchdog uses a single global 'wd_hw_attr' variable > > to serve perf event attributes and once p4_hw_watchdog_set_attr > > has modified it subsequent calls on the rest cpus trigger > > the warning. > > > > It is safe to simply drop it since we know the caller may > > pass already altered type and config. > > > > Repoted-by: Steven Rostedt > > Repoted? Hmm, maybe symbolically I put this code in a different pot. > > Reported-and-tested-by: Steven Rostedt > Oh, really sorry, Steven :/ Fingers... Just to have all in place. --- perf, x86: P4 PMU - Drop redundant WARN_ON_ONCE This WARN_ON_ONCE triggers a false alarm on SMP because nmi-watchdog uses a single global 'wd_hw_attr' variable to serve perf event attributes and once p4_hw_watchdog_set_attr has modified it subsequent calls on the rest cpus trigger the warning. It is safe to simply drop it since we know the caller may pass already altered type and config. Reported-and-tested-by: Steven Rostedt Signed-off-by: Cyrill Gorcunov --- arch/x86/kernel/cpu/perf_event_p4.c | 3 --- 1 file changed, 3 deletions(-) Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c =================================================================== --- linux-2.6.git.orig/arch/x86/kernel/cpu/perf_event_p4.c +++ linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c @@ -726,9 +726,6 @@ static void p4_hw_watchdog_set_attr(stru * that named "non-sleeping" ticks as recommended * by Intel SDM Vol3b. */ - WARN_ON_ONCE(wd_attr->type != PERF_TYPE_HARDWARE || - wd_attr->config != PERF_COUNT_HW_CPU_CYCLES); - wd_attr->type = PERF_TYPE_RAW; wd_attr->config = p4_config_pack_escr(P4_ESCR_EVENT(P4_EVENT_EXECUTION_EVENT) |