From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751602Ab2BUXaz (ORCPT ); Tue, 21 Feb 2012 18:30:55 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:55909 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751134Ab2BUXay (ORCPT ); Tue, 21 Feb 2012 18:30:54 -0500 Date: Tue, 21 Feb 2012 15:30:31 -0800 From: "Paul E. McKenney" To: Peter Zijlstra 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 Subject: Re: [PATCH tip/core/rcu 3/4] rcu: stop spurious warnings from synchronize_sched_expedited Message-ID: <20120221233031.GU2375@linux.vnet.ibm.com> Reply-To: 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> <1329847217.2293.417.camel@twins> <20120221182804.GK2375@linux.vnet.ibm.com> <1329850623.2293.419.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1329850623.2293.419.camel@twins> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12022123-6148-0000-0000-000003A3B55F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 21, 2012 at 07:57:03PM +0100, Peter Zijlstra wrote: > On Tue, 2012-02-21 at 10:28 -0800, Paul E. McKenney wrote: > > On Tue, Feb 21, 2012 at 07:00:17PM +0100, Peter Zijlstra wrote: > > > 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.. > > > > The check was already there, Hugh simply fixed it to use raw_. The check > > itself was added in c0d6d01bf (Check for illegal use of RCU from offlined > > CPUs). The purpose is to catch improper use of RCU from CPU_DYING > > notifiers and on the path from the CPU_DYING notifiers to the idle loop. > > Then I think this patch wants to add a comment explaining this. Because > cpu_offline(raw_smp_processor_id()) looks really rather suspicious. Good point, will fix! Thanx, Paul