From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934440AbcCNOo5 (ORCPT ); Mon, 14 Mar 2016 10:44:57 -0400 Received: from e06smtp13.uk.ibm.com ([195.75.94.109]:45445 "EHLO e06smtp13.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934339AbcCNOoz (ORCPT ); Mon, 14 Mar 2016 10:44:55 -0400 X-IBM-Helo: d06dlp01.portsmouth.uk.ibm.com X-IBM-MailFrom: brueckner@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org;linux-s390@vger.kernel.org Date: Mon, 14 Mar 2016 15:44:50 +0100 From: Hendrik Brueckner To: Heiko Carstens Cc: Anna-Maria Gleixner , Hendrik Brueckner , linux-kernel@vger.kernel.org, rt@linutronix.de, Martin Schwidefsky , linux-s390@vger.kernel.org Subject: Re: [PATCH 2/2] s390/cpum_sf: Fix cpu hotplug notifier transitions Message-ID: <20160314144450.GA5628@linux.vnet.ibm.com> Mail-Followup-To: Heiko Carstens , Anna-Maria Gleixner , linux-kernel@vger.kernel.org, rt@linutronix.de, Martin Schwidefsky , linux-s390@vger.kernel.org References: <1457693558-45970-1-git-send-email-anna-maria@linutronix.de> <1457693558-45970-3-git-send-email-anna-maria@linutronix.de> <20160314085150.GA5346@osiris> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160314085150.GA5346@osiris> User-Agent: Mutt/1.5.20 (2009-12-10) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16031414-0013-0000-0000-0000091677D3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 14, 2016 at 09:51:50AM +0100, Heiko Carstens wrote: > On Fri, Mar 11, 2016 at 11:52:38AM +0100, Anna-Maria Gleixner wrote: > > The cpumf_pmu_notfier() hotplug callback lacks handling of the > > CPU_DOWN_FAILED case. That means, if CPU_DOWN_PREPARE failes, the PMC > > of the CPU is not setup again. Furthermore the CPU_ONLINE_FROZEN case > > will never be processed because of masking the switch expression with > > CPU_TASKS_FROZEN. > > > > Add handling for CPU_DOWN_FAILED transition to setup the PMC of the > > CPU. Remove CPU_ONLINE_FROZEN case. > > > > 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 | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > --- a/arch/s390/kernel/perf_cpum_sf.c > > +++ b/arch/s390/kernel/perf_cpum_sf.c > > @@ -1518,7 +1518,7 @@ static int cpumf_pmu_notifier(struct not > > > > switch (action & ~CPU_TASKS_FROZEN) { > > case CPU_ONLINE: > > - case CPU_ONLINE_FROZEN: > > + case CPU_DOWN_FAILED: The change looks ok for me. Acked-by: Hendrik Brueckner > > flags = PMC_INIT; > > smp_call_function_single(cpu, setup_pmc_cpu, &flags, 1); > > break; > > This is a bit odd, but independent from your patch: setup_pmc_cpu() will > only deallocate buffers but not allocate them. That's right. Allocation is done when an perf event is about to be scheduled on a CPU. > > Looking at the code a bit further this seems to imply that sampling will > not work on cpus that were added later. That might be a problem for task-based perf events. I will have a closer look into that issue. Many thanks. Kind regards, Hendrik