From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758140Ab3KIBJU (ORCPT ); Fri, 8 Nov 2013 20:09:20 -0500 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.225]:20274 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757850Ab3KIBJS (ORCPT ); Fri, 8 Nov 2013 20:09:18 -0500 Date: Fri, 8 Nov 2013 20:09:05 -0500 From: Steven Rostedt To: Frederic Weisbecker Cc: Vince Weaver , LKML , Ingo Molnar , Peter Zijlstra , Dave Jones Subject: Re: perf/tracepoint: another fuzzer generated lockup Message-ID: <20131108200905.3bdb15d9@gandalf.local.home> In-Reply-To: <20131108223657.GF14606@localhost.localdomain> References: <20131108200244.GB14606@localhost.localdomain> <20131108204839.GD14606@localhost.localdomain> <20131108223657.GF14606@localhost.localdomain> X-Mailer: Claws Mail 3.9.2 (GTK+ 2.24.20; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.118:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 8 Nov 2013 23:36:58 +0100 Frederic Weisbecker wrote: > [ 237.623178] ---[ end trace 40cda30d05d0ffa6 ]--- > [ 237.627769] perf samples too long (3397569 > 2500), lowering kernel.perf_event_max_sample_rate to 50000 > [ 237.637124] INFO: NMI handler (perf_event_nmi_handler) took too long to run: 444.233 msecs > > 444 msecs is huge. I don't think that's the issue you are looking for. Peter told me there's a timer race with overflows or something (I don't remember the details, Peter can clarify it), that causes the second timestamp to be bogus compared to the first, and this makes the code think that the NMI handler was running much longer that it actually was. -- Steve > > [ 247.186562] perf samples too long (3371028 > 5000), lowering kernel.perf_event_max_sample_rate to 25000 > [ 257.180241] perf samples too long (3344694 > 10000), lowering kernel.perf_event_max_sample_rate to 13000 > [ 267.173920] perf samples too long (3318566 > 19230), lowering kernel.perf_event_max_sample_rate to 7000 > [ 277.167598] perf samples too long (3292642 > 35714), lowering kernel.perf_event_max_sample_rate to 4000 > [ 287.161277] perf samples too long (3266920 > 62500), lowering kernel.perf_event_max_sample_rate to 2000 > [ 297.154956] perf samples too long (3241400 > 125000), lowering kernel.perf_event_max_sample_rate to 1000