From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754091Ab0JPLMm (ORCPT ); Sat, 16 Oct 2010 07:12:42 -0400 Received: from arkanian.console-pimps.org ([212.110.184.194]:36310 "EHLO arkanian.console-pimps.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753800Ab0JPLMk (ORCPT ); Sat, 16 Oct 2010 07:12:40 -0400 Date: Sat, 16 Oct 2010 12:12:38 +0100 From: Matt Fleming To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Arnaldo Carvalho de Melo , Frederic Weisbecker Subject: Re: [PATCH] perf: Detach group events when removing event from ctx Message-ID: <20101016111238.GA7806@console-pimps.org> References: <8e7ce03ad7d5f94290a4e865c1fe5f7f7279e27f.1286134285.git.matt@console-pimps.org> <1287135757.29097.1368.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1287135757.29097.1368.camel@twins> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 15, 2010 at 11:42:37AM +0200, Peter Zijlstra wrote: > On Sun, 2010-10-03 at 20:35 +0100, Matt Fleming wrote: > > When removing an event from a task's list of events we need to make sure > > that we also detach all group events. If we don't, then when we later > > call perf_group_attach() we'll hit the WARN_ON_ONCE() like so, > > > > [ 1200.449161] ------------[ cut here ]------------ > > [ 1200.449171] WARNING: at kernel/perf_event.c:313 add_event_to_ctx+0xe1/0x159() > > [ 1200.449174] Hardware name: MacBook2,1 > > [ 1200.449176] Modules linked in: dm_mod sg sd_mod > > [ 1200.449183] Pid: 7619, comm: perf Not tainted 2.6.36-rc6-tip+ #2 > > [ 1200.449186] Call Trace: > > [ 1200.449193] [] warn_slowpath_common+0x85/0x9d > > [ 1200.449197] [] warn_slowpath_null+0x1a/0x1c > > [ 1200.449201] [] add_event_to_ctx+0xe1/0x159 > > [ 1200.449206] [] perf_install_in_context+0x85/0x99 > > [ 1200.449210] [] sys_perf_event_open+0x4da/0x633 > > [ 1200.449216] [] system_call_fastpath+0x16/0x1b > > [ 1200.449218] ---[ end trace 9df38c30c6cacb50 ]--- > > I think its due to the new and fancy move groups around context code > from: b04243ef70 (perf: Complete software pmu grouping). > > Does the below cure it? > > It only detaches the group when we move it from one context to another, > the perf_install_in_context() later on will then re-assemble the group > on the other context. > > --- > Index: linux-2.6/kernel/perf_event.c > =================================================================== > --- linux-2.6.orig/kernel/perf_event.c > +++ linux-2.6/kernel/perf_event.c > @@ -5592,6 +5592,7 @@ SYSCALL_DEFINE5(perf_event_open, > list_for_each_entry(sibling, &group_leader->sibling_list, > group_entry) { > perf_event_remove_from_context(sibling); > + perf_group_detach(sibling); > put_ctx(gctx); > } > mutex_unlock(&gctx->mutex); > Unfortunately this still hits the WARN_ON_ONCE() :-(