From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753903AbbDHOO3 (ORCPT ); Wed, 8 Apr 2015 10:14:29 -0400 Received: from casper.infradead.org ([85.118.1.10]:47495 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751376AbbDHOO1 (ORCPT ); Wed, 8 Apr 2015 10:14:27 -0400 Date: Wed, 8 Apr 2015 11:14:27 -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: <20150408141427.GE5403@kernel.org> References: <20150408134251.GC5403@kernel.org> <20150408134545.GD5403@kernel.org> <552531A7.9070605@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <552531A7.9070605@gmail.com> 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 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 - Arnaldo