Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753301Ab3COBGn (ORCPT ); Thu, 14 Mar 2013 21:06:43 -0400 Received: from mail-vc0-f172.google.com ([209.85.220.172]:57893 "EHLO mail-vc0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751626Ab3COBGl (ORCPT ); Thu, 14 Mar 2013 21:06:41 -0400 MIME-Version: 1.0 In-Reply-To: References: <20130226070247.GA14094@gmail.com> Date: Thu, 14 Mar 2013 18:06:41 -0700 X-Google-Sender-Auth: q9ExkV5fRgSrDcOpU_1Oukg8E5E Message-ID: Subject: Re: [GIT PULL] perf fixes From: Linus Torvalds To: Stephane Eranian Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Peter Zijlstra , Thomas Gleixner , Andrew Morton , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1714 Lines: 42 On Thu, Mar 14, 2013 at 5:24 PM, Stephane Eranian wrote: > > I bet if you force the affinity of your perf record to be on > a CPU other than CPU0, you will not get the crash. > > This is what I am seeing now. I appears on resume, > CPU0 hotplug callbacks for perf_events are not invoked > leaving DS_AREA MSR to 0. > > Can you confirm on your machine? I'm not even going to bother confirming it, because I think you're right, and I think the reason is clear: the DS initialization code uses the CPU_UP notifiers. And that's sufficient for CPU hotplug, which is what suspend/resume ends up doing for all but the boot CPU. But the boot CPU is not hotplugged. Using CPU_UP notifiers is wrong, and they get called too late anyway. The code should use a real resume method. Or, better yet, just do it right, and do it from __restore_processor_state(). Those f*cking CPU notifiers are a pain in the ass, and the tend to be invariably broken, and they have their own idiotic hacks that are equally broken (ie that x86_pmu_notifier() thing seems to make up its own suspend/resume with "x86_pmu.cpu_prepare/cpu_starting/cpu_dying/cpu_dead" things. I guess we could make the BP do a fake cpu notifier thing around the suspend of the boot processor as well, but most of the per-CPU stuff seems to be perfectly fine without it (ie mtrr, apic, etc etc all use the suspend/resume infrastructure) and doesn't need that kind of stuff. Linus -- 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/