Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935463AbZJOUUN (ORCPT ); Thu, 15 Oct 2009 16:20:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S935384AbZJOUUM (ORCPT ); Thu, 15 Oct 2009 16:20:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:7820 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933196AbZJOUUK (ORCPT ); Thu, 15 Oct 2009 16:20:10 -0400 Date: Thu, 15 Oct 2009 22:19:16 +0200 (CEST) From: John Kacur X-X-Sender: jkacur@localhost.localdomain To: Joerg.Abraham@alcatel-lucent.de, linux-kernel@vger.kernel.org cc: Thomas Gleixner , Ingo Molnar , linux-rt-users@vger.kernel.org Subject: Re: 2.6.31.4-rt14 posix message queues problem In-Reply-To: Message-ID: References: <4AD76126.1000408@alcatel-lucent.de> <520f0cf10910151202k2ba01453r10e96eeb064232e8@mail.gmail.com> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2676 Lines: 85 On Thu, 15 Oct 2009, John Kacur wrote: > > > From: Joerg Abraham > > Date: Thu, Oct 15, 2009 at 7:51 PM > > Subject: 2.6.31.4-rt14 posix message queues problem > > To: LKML > > > > > > Hi, > > > > During some performance measurement I stumbled over unexpected bad > > results for a posix message queue test case. Which is not surprising > > since the kernel log shows a "BUG: scheduling while atomic:" on every > > measurement trigger. > > > > Attached is the kernel log for an embedded 8572ds powerpc system and a > > condensed user space test appli. The test appli uses 2 processes > > (mq_server and mq_client) and pingpongs some messages via posix > > message queues. Please see the c-file header for details (the appli > > itself makes not much sense but shows the problem). > > > > ./mq_server > > ./mq_client # just crashes during run > > > > The problem does _not_ occur on kernels 2.6.29.6-rt24, 2.6.29.6 > > vanilla and 2.6.31.4 vanilla. The problem does _also_ show up on an > > embedded x86_64 system and a full featured fc11 x86_64 system running > > a 2.6.31.4-rt14 based kernel, so I dont think it's arch dependent. > > > > Can anybody reproduce the crash ??? > > > > If you need more info's please let me know. > > > > [And if I'm doing stupid things just forgive me] > > > > Thanx > > > > Joerg > > Hello Joerg > > Does the following patch solve your problem? > > From 69fde4357db4a054733cbca4158606160e821a3a Mon Sep 17 00:00:00 2001 > From: John Kacur > Date: Thu, 15 Oct 2009 20:52:37 +0200 > Subject: [PATCH] preempt_disable_rt(); should be paired with preempt_enable_rt() > > Signed-off-by: John Kacur > --- > ipc/mqueue.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/ipc/mqueue.c b/ipc/mqueue.c > index 63a47f7..ab4df36 100644 > --- a/ipc/mqueue.c > +++ b/ipc/mqueue.c > @@ -830,7 +830,7 @@ static inline void pipelined_send(struct mqueue_inode_info *info, > wake_up_process(receiver->task); > smp_wmb(); > receiver->state = STATE_READY; > - preempt_enable_nort(); > + preempt_enable_rt(); > } > > /* pipelined_receive() - if there is task waiting in sys_mq_timedsend() > -- > 1.6.0.6 > > fyi: I completed my testing, and I was able to reproduce your problem on v2.6.31.4-rt14, and it goes away with the above patch. Cheers John -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/