From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758058Ab3KHUsp (ORCPT ); Fri, 8 Nov 2013 15:48:45 -0500 Received: from mail-wi0-f174.google.com ([209.85.212.174]:43880 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757583Ab3KHUso (ORCPT ); Fri, 8 Nov 2013 15:48:44 -0500 Date: Fri, 8 Nov 2013 21:48:41 +0100 From: Frederic Weisbecker To: Vince Weaver Cc: Steven Rostedt , LKML , Ingo Molnar , Peter Zijlstra , Dave Jones Subject: Re: perf/tracepoint: another fuzzer generated lockup Message-ID: <20131108204839.GD14606@localhost.localdomain> References: <20131108200244.GB14606@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 On Fri, Nov 08, 2013 at 03:23:07PM -0500, Vince Weaver wrote: > On Fri, 8 Nov 2013, Frederic Weisbecker wrote: > > > > There seem to be a loop that takes too long in intel_pmu_handle_irq(). Your two > > previous reports seemed to suggest that lbr is involved, but not this one. > > I may be wrong but I think everything between and is just > noise from the NMI perf-event watchdog timer kicking in. Ah good point. So the pattern seem to be that irq work/perf_event_wakeup is involved, may be interrupting a tracepoint event or so. It would be nice if you enable CONFIG_FRAME_POINTER in your future reports so that we get more precise traces. Or may be you actually enabled it and it doesn't work? > Why that code would be reading the LBR registers I don't know. Yeah that's just an inconditional call to check if there is lbr branch to record. > Vince > >