Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757979AbcDEKtZ (ORCPT ); Tue, 5 Apr 2016 06:49:25 -0400 Received: from e06smtp15.uk.ibm.com ([195.75.94.111]:56577 "EHLO e06smtp15.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757928AbcDEKtY (ORCPT ); Tue, 5 Apr 2016 06:49:24 -0400 X-IBM-Helo: d06dlp01.portsmouth.uk.ibm.com X-IBM-MailFrom: heiko.carstens@de.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org;linux-s390@vger.kernel.org Date: Tue, 5 Apr 2016 12:49:12 +0200 From: Heiko Carstens To: Anna-Maria Gleixner Cc: linux-kernel@vger.kernel.org, rt@linutronix.de, Martin Schwidefsky , linux-s390@vger.kernel.org Subject: Re: [PATCH] s390/cpum_sf: Remove superfluous SMP function call Message-ID: <20160405104912.GC3937@osiris> References: <1459765640-13599-1-git-send-email-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1459765640-13599-1-git-send-email-anna-maria@linutronix.de> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16040510-0021-0000-0000-00002F6E484C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1585 Lines: 40 On Mon, Apr 04, 2016 at 12:27:20PM +0200, Anna-Maria Gleixner wrote: > Since commit 1cf4f629d9d2 ("cpu/hotplug: Move online calls to > hotplugged cpu") it is ensured that callbacks of CPU_ONLINE and > CPU_DOWN_PREPARE are processed on the hotplugged CPU. Due to this SMP > function calls are no longer required. > > Replace smp_call_function_single() with a direct call of > setup_pmc_cpu(). To keep the calling convention, interrupts are > explicitely disabled around the call. > > Cc: Martin Schwidefsky > Cc: Heiko Carstens > Cc: linux-s390@vger.kernel.org > Signed-off-by: Anna-Maria Gleixner > --- > arch/s390/kernel/perf_cpum_sf.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > --- a/arch/s390/kernel/perf_cpum_sf.c > +++ b/arch/s390/kernel/perf_cpum_sf.c > @@ -1510,7 +1510,6 @@ static void cpumf_measurement_alert(stru > static int cpumf_pmu_notifier(struct notifier_block *self, > unsigned long action, void *hcpu) > { > - unsigned int cpu = (long) hcpu; > int flags; > > /* Ignore the notification if no events are scheduled on the PMU. > @@ -1523,11 +1522,15 @@ static int cpumf_pmu_notifier(struct not > case CPU_ONLINE: > case CPU_DOWN_FAILED: > flags = PMC_INIT; > - smp_call_function_single(cpu, setup_pmc_cpu, &flags, 1); > + local_irq_disable(); > + setup_pmc_cpu(&flags); > + local_irq_enable(); > break; ...but at least the CPU_DOWN_FAILED callback will not necessarily be called on the cpu that couldn't be brought offline.