From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755868Ab2JPSp7 (ORCPT ); Tue, 16 Oct 2012 14:45:59 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:44477 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755796Ab2JPSp6 (ORCPT ); Tue, 16 Oct 2012 14:45:58 -0400 Date: Tue, 16 Oct 2012 11:34:31 -0700 From: "Paul E. McKenney" To: "Srivatsa S. Bhat" Cc: peterz@infradead.org, acme@ghostprotocols.net, mingo@kernel.org, tglx@linutronix.de, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [RESEND PATCH 1/2] perf, cpu hotplug: Run CPU_STARTING notifiers with irqs disabled Message-ID: <20121016183431.GF2385@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20121016075809.3572.47848.stgit@srivatsabhat.in.ibm.com> <20121016163140.GA2385@linux.vnet.ibm.com> <507D8D3B.5000506@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <507D8D3B.5000506@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12101618-2876-0000-0000-000001176346 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 16, 2012 at 10:07:15PM +0530, Srivatsa S. Bhat wrote: > On 10/16/2012 10:01 PM, Paul E. McKenney wrote: > > On Tue, Oct 16, 2012 at 01:28:10PM +0530, Srivatsa S. Bhat wrote: > >> The CPU_STARTING notifiers are supposed to be run with irqs disabled. But the > >> perf_cpu_notifier() macro invokes them without doing that. Fix it. > > > > Color me confused... > > Hehe, I believe the context provided by diff tricked you ;-) > The function I am referring to is perf_cpu_notifier(), not > perf_event_task_tick() :-) It did indeed fool me! And indeed, checking the code did indeed show that the name of interest if perf_cpu_notifier(). When using the correct name, I do indeed find places where it is called with interrupts enabled. So... Reviewed-by: Paul E. McKenney > Regards, > Srivatsa S. Bhat > > > Isn't perf_event_task_tick() invoked only > > from scheduler_tick(), which always has interrupts disabled? > > > > Or are you needing to invoke it from somewhere else? > > > > Thanx, Paul > > > >> Signed-off-by: Srivatsa S. Bhat > >> --- > >> > >> include/linux/perf_event.h | 3 +++ > >> 1 file changed, 3 insertions(+) > >> > >> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > >> index 2e90235..0647805 100644 > >> --- a/include/linux/perf_event.h > >> +++ b/include/linux/perf_event.h > >> @@ -803,10 +803,13 @@ static inline void perf_event_task_tick(void) { } > >> do { \ > >> static struct notifier_block fn##_nb __cpuinitdata = \ > >> { .notifier_call = fn, .priority = CPU_PRI_PERF }; \ > >> + unsigned long flags; \ > >> fn(&fn##_nb, (unsigned long)CPU_UP_PREPARE, \ > >> (void *)(unsigned long)smp_processor_id()); \ > >> + local_irq_save(flags); \ > >> fn(&fn##_nb, (unsigned long)CPU_STARTING, \ > >> (void *)(unsigned long)smp_processor_id()); \ > >> + local_irq_restore(flags); \ > >> fn(&fn##_nb, (unsigned long)CPU_ONLINE, \ > >> (void *)(unsigned long)smp_processor_id()); \ > >> register_cpu_notifier(&fn##_nb); \ > >> >