From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754401AbbDHOhN (ORCPT ); Wed, 8 Apr 2015 10:37:13 -0400 Received: from casper.infradead.org ([85.118.1.10]:47625 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754319AbbDHOhL (ORCPT ); Wed, 8 Apr 2015 10:37:11 -0400 Date: Wed, 8 Apr 2015 11:37:12 -0300 From: Arnaldo Carvalho de Melo To: David Ahern Cc: Linux Kernel Mailing List , Don Zickus , Jiri Olsa , Joe Mario , Ingo Molnar Subject: Re: BUG: perf top enters loop synthesizing events for existing threads Message-ID: <20150408143712.GH5403@kernel.org> References: <20150408134251.GC5403@kernel.org> <20150408134545.GD5403@kernel.org> <552531A7.9070605@gmail.com> <20150408141427.GE5403@kernel.org> <20150408143437.GG5403@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150408143437.GG5403@kernel.org> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Wed, Apr 08, 2015 at 11:34:37AM -0300, Arnaldo Carvalho de Melo escreveu: > Em Wed, Apr 08, 2015 at 11:14:27AM -0300, Arnaldo Carvalho de Melo escreveu: > > Em Wed, Apr 08, 2015 at 07:48:23AM -0600, David Ahern escreveu: > > > On 4/8/15 7:45 AM, Arnaldo Carvalho de Melo wrote: > > > >>I also noticed that if I set /proc/sys/kernel/perf_event_paranoid to -1 > > > >>to run it as !root, then the problem "goes away", which I think probably > > > >>is explained by, as !root, not being able to parse some of the /proc > > > >>files for existing threads and thus not triggering the bug, still > > > >>investigating... > > > > > > odd. because this has nothing to do with perf_events; it is just walking > > > /proc and for the ppid adds a strstr and atoi(str). Something else is at > > > play. I'll take a look. > > > > You are correcly setting the pid values, that will have effects when > > using findnew, i.e. threads will be added to the rbtree, which causes > > allocations, etc I.e. it is probably triggering a dormant bug > > Sitting there, will stop chrome to see if the problem is triggered by it... Yeah, stopping chrome gets the system to a state that doesn't make it trigger the bug, why it works when your patch is reverted still a puzzle... - Arnaldo