From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762666AbYBAXnr (ORCPT ); Fri, 1 Feb 2008 18:43:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761577AbYBAXni (ORCPT ); Fri, 1 Feb 2008 18:43:38 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:33334 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760170AbYBAXnh (ORCPT ); Fri, 1 Feb 2008 18:43:37 -0500 From: "Rafael J. Wysocki" To: Peter Zijlstra Subject: Re: [Regression] 2.6.24-git9: RT sched mishandles artswrapper (bisected) Date: Sat, 2 Feb 2008 00:39:58 +0100 User-Agent: KMail/1.9.6 (enterprise 20070904.708012) Cc: Ingo Molnar , Steven Rostedt , LKML , Andrew Morton References: <200802010237.59320.rjw@sisk.pl> <200802011250.18699.rjw@sisk.pl> <1201867797.32654.52.camel@lappy> In-Reply-To: <1201867797.32654.52.camel@lappy> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200802020040.05519.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday, 1 of February 2008, Peter Zijlstra wrote: > > On Fri, 2008-02-01 at 12:50 +0100, Rafael J. Wysocki wrote: > > On Friday, 1 of February 2008, Peter Zijlstra wrote: > > > > > It arts run as root, or does it use RLIMIT_RTPRIO to allow users to > > > > execute realtime tasks? > > > > artswrapper is setuid root and RLIMIT_RTPRIO is apparently not used. > > Still, artswrapper is running as a regular user, so it most probably drops > > privileges early. > > > > BTW, it fails while running the artsmessage utility used for displaying arts > > error messages, so I guess there's an error in arts that this thing tries to > > display and deadlocks (or something like that). > > > > Should I test the patch nevertheless? > > Don't think that would help any in this situation. The thing to look out > for are RT tasks running with a different uid than 0. > > This patch would only stop a task from obtaining RT class scheduling > when already in a (misconfigured) group. If the task is RT and then > switches group another - similar - thing is needed. > > Does this artsmessage thing also run with RT priority? Well, it's in a strange state (after it's broken). From top: PR = -51 NI = 0 S = R %CPU = 0.0 %MEM = 0.0 Here's the corresponding trace from sysrq+t: artswrapper R running task 5128 5776 1 ffff81007a8dbd88 0000000000000046 000000015c4321b0 ffff81006aa6e5c8 ffffffff806daa00 ffffffff806daa00 ffffffff806daa00 ffffffff806daa00 ffffffff806daa00 ffffffff806daa00 ffffffff806d7a60 ffffffff806daa00 Call Trace: [] ? try_to_wake_up+0x77/0x200 [] __cond_resched+0x2d/0x60 [] _cond_resched+0x31/0x40 [] wait_for_common+0x34/0x170 [] ? try_to_wake_up+0x77/0x200 [] wait_for_completion+0x18/0x20 [] sched_exec+0xba/0xf0 [] do_execve+0x64/0x220 [] sys_execve+0x46/0x70 [] stub_execve+0x67/0xb0