From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 5733 invoked by alias); 27 May 2009 21:02:13 -0000 Received: (qmail 4309 invoked by uid 22791); 27 May 2009 21:02:09 -0000 X-SWARE-Spam-Status: No, hits=-2.2 required=5.0 tests=AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from e2.ny.us.ibm.com (HELO e2.ny.us.ibm.com) (32.97.182.142) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 27 May 2009 21:02:02 +0000 Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by e2.ny.us.ibm.com (8.13.1/8.13.1) with ESMTP id n4RKvlg4016518 for ; Wed, 27 May 2009 16:57:47 -0400 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay02.pok.ibm.com (8.13.8/8.13.8/NCO v9.2) with ESMTP id n4RL20mm247258 for ; Wed, 27 May 2009 17:02:00 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n4RL1xM9006958 for ; Wed, 27 May 2009 17:02:00 -0400 Received: from paulmck-laptop.localdomain (paulmck-laptop-009047022066.beaverton.ibm.com [9.47.22.66]) by d01av04.pok.ibm.com (8.12.11.20060308/8.12.11) with ESMTP id n4RL1xb6006926; Wed, 27 May 2009 17:01:59 -0400 Received: by paulmck-laptop.localdomain (Postfix, from userid 1000) id E707414FBD4; Wed, 27 May 2009 14:01:59 -0700 (PDT) Date: Wed, 27 May 2009 21:02:00 -0000 From: "Paul E. McKenney" To: Darren Hart Cc: Josh Stone , Kiran , systemtap@sources.redhat.com, sripathi@in.ibm.com, jkenisto@us.ibm.com Subject: Re: BUG: [preempt-rt] scheduling while atomic: stapio Message-ID: <20090527210159.GF6729@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1242812648.13247.12.camel@kiran-laptop> <4A145856.6080303@redhat.com> <4A1D6DAA.9010608@us.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A1D6DAA.9010608@us.ibm.com> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2009-q2/txt/msg00719.txt.bz2 On Wed, May 27, 2009 at 09:43:22AM -0700, Darren Hart wrote: > Josh Stone wrote: >> On 05/20/2009 02:44 AM, Kiran wrote: >>> BUG: scheduling while atomic: stapio/0x00000001/26142, CPU#3 >>> [...] >>> [] cpufreq_unregister_notifier+0x35/0x5c >>> [] _stp_kill_time+0xb6/0xbd >>> [stap_246f93f30a500769142af9987624737a_5072] >>> [] probe_1391+0x3c/0xa8 >>> [stap_246f93f30a500769142af9987624737a_5072] >>> [] enter_end_probe+0x14a/0x1e3 >>> [stap_246f93f30a500769142af9987624737a_5072] >> enter_end_probe will call preempt_disable, and apparently the call path >> from cpufreq_unregister_notifier can sleep. Is this true only of the RT >> kernel? > > The call into the __synchronize_sched() from synchronize_rcu() appears to > be able to sleep regardless of -rt. It's possible -rt is more likely to > make them sleep. One would expect __synchronize_sched() to sleep, except on non-rt uniprocessor systems. So a uniprocessor system might well see this only when running -rt. Thanx, Paul