From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755407Ab1A1Sgz (ORCPT ); Fri, 28 Jan 2011 13:36:55 -0500 Received: from mail.openrapids.net ([64.15.138.104]:57772 "EHLO blackscsi.openrapids.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753199Ab1A1Sgy (ORCPT ); Fri, 28 Jan 2011 13:36:54 -0500 Date: Fri, 28 Jan 2011 13:36:50 -0500 From: Mathieu Desnoyers To: Anca Emanuel Cc: Thomas Gleixner , Ingo Molnar , Tejun Heo , roland@redhat.com, oleg@redhat.com, jan.kratochvil@redhat.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, Peter Zijlstra , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker Subject: Re: [PATCHSET] ptrace,signal: group stop / ptrace updates Message-ID: <20110128183650.GA26633@Krystal> References: <1296227324-25295-1-git-send-email-tj@kernel.org> <20110128165455.GA18194@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Editor: vi X-Info: http://www.efficios.com X-Operating-System: Linux/2.6.26-2-686 (i686) X-Uptime: 13:29:41 up 65 days, 23:32, 1 user, load average: 0.19, 0.09, 0.05 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Anca Emanuel (anca.emanuel@gmail.com) wrote: > On Fri, Jan 28, 2011 at 7:41 PM, Thomas Gleixner wrote: > > On Fri, 28 Jan 2011, Ingo Molnar wrote: > >> See that '^C^C' line? That is where i had to do Ctrl-C twice. > >> > >> It only fails here about once every 10 times, so it's very rare. I have a stock F14 > >> system running on that box, with the very latest .38 based kernel. > > > > Tripped over the refuse ^C thing today twice. Had to kill a kernel > > build from another shell. It just happily displayed ^C and never > > stopped. That happens once in a while and I have no idea either how to > > debug that. > > cc: Mathieu > > Use lttng ? Heh :) I'm sure Ingo and Thomas have their own tools for that ;) There is one extra thing in the LTTng instrumentation that can help solve this problem: the "input subsystem" instrumentation (enabled with ltt-armall -i). You can then get a dump of: - Your keystrokes (you can then grep for your ctrl-c input) - Read/poll/select system calls (so you know when your terminal receives the input). - Signals sent/delivered Some of these are already instrumented in the mainline kernel, so you might get away without the input subsystem instrumentation. If I had to take a wild guess, my bet would be to take a look in the area of signal delivery, but you never know, maybe it's a userspace bug in the X terminal emulator code that is causing this weirdness. Hope this helps, Mathieu -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com