Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754288Ab3HPQep (ORCPT ); Fri, 16 Aug 2013 12:34:45 -0400 Received: from mail-wg0-f41.google.com ([74.125.82.41]:55502 "EHLO mail-wg0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752439Ab3HPQem (ORCPT ); Fri, 16 Aug 2013 12:34:42 -0400 Date: Fri, 16 Aug 2013 18:34:39 +0200 From: Frederic Weisbecker To: Oleg Nesterov Cc: Peter Zijlstra , LKML , Fernando Luis Vazquez Cao , Tetsuo Handa , Thomas Gleixner , Ingo Molnar , Andrew Morton , Arjan van de Ven Subject: Re: [PATCH 4/4] nohz: Convert a few places to use local per cpu accesses Message-ID: <20130816163437.GG24210@somewhere> References: <1376667753-29014-1-git-send-email-fweisbec@gmail.com> <1376667753-29014-5-git-send-email-fweisbec@gmail.com> <20130816160043.GA24092@twins.programming.kicks-ass.net> <20130816161954.GA32704@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130816161954.GA32704@redhat.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 Content-Length: 1481 Lines: 38 On Fri, Aug 16, 2013 at 06:19:54PM +0200, Oleg Nesterov wrote: > On 08/16, Peter Zijlstra wrote: > > > > OK so these patches look ok to me -- didn't read in detail though. > > > > On Fri, Aug 16, 2013 at 05:42:33PM +0200, Frederic Weisbecker wrote: > > > A few functions use remote per CPU access APIs when they > > > deal with local values. > > > > > > Just to the right conversion to improve performance, code > > > readability and debug checks. > > > > > @@ -410,7 +408,7 @@ static void tick_nohz_update_jiffies(ktime_t now) > > > > > > static void tick_nohz_stop_idle(int cpu, ktime_t now) > > > { > > > - struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); > > > + struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); > > > > What's there from stopping someone from calling this with cpu != > > smp_processor_id() ? > > I _guess_ this should not happen, but in this case we should probably > remove the "cpu" argument. And smp_processor_id() in tick_nohz_idle_exit(). > > tick_check_idle/tick_check_nohz doesn't need "int cpu" too, it seems. Yep, indeed it seems right to remove the cpu argument to prevent from further calls to these APIs on remote CPUs, which would otherwise result in random disaster. > > Oleg. > -- 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/