From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755065Ab2BUSBF (ORCPT ); Tue, 21 Feb 2012 13:01:05 -0500 Received: from merlin.infradead.org ([205.233.59.134]:43708 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752225Ab2BUSAs convert rfc822-to-8bit (ORCPT ); Tue, 21 Feb 2012 13:00:48 -0500 Message-ID: <1329847217.2293.417.camel@twins> Subject: Re: [PATCH tip/core/rcu 3/4] rcu: stop spurious warnings from synchronize_sched_expedited From: Peter Zijlstra To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org, Hugh Dickins Date: Tue, 21 Feb 2012 19:00:17 +0100 In-Reply-To: <1329847110-10897-3-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120221175810.GA10708@linux.vnet.ibm.com> <1329847110-10897-1-git-send-email-paulmck@linux.vnet.ibm.com> <1329847110-10897-3-git-send-email-paulmck@linux.vnet.ibm.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-02-21 at 09:58 -0800, Paul E. McKenney wrote: > From: Hugh Dickins > > synchronize_sched_expedited() is spamming CONFIG_DEBUG_PREEMPT=y > users with an unintended warning from the cpu_is_offline() check: > use raw_smp_processor_id() instead of smp_processor_id() there. This fails to mention why it makes sense to test a random cpu for offline-ness.. > Signed-off-by: Hugh Dickins > Signed-off-by: Paul E. McKenney > --- > kernel/rcutree.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index eacc10b..1050d6d 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -2014,7 +2014,7 @@ void synchronize_sched_expedited(void) > /* Note that atomic_inc_return() implies full memory barrier. */ > firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started); > get_online_cpus(); > - WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); > + WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id())); > > /* > * Each pass through the following loop attempts to force a