From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965995AbXDJA1F (ORCPT ); Mon, 9 Apr 2007 20:27:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932359AbXDJA1E (ORCPT ); Mon, 9 Apr 2007 20:27:04 -0400 Received: from smtp.osdl.org ([65.172.181.24]:38403 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932344AbXDJA1B (ORCPT ); Mon, 9 Apr 2007 20:27:01 -0400 Date: Mon, 9 Apr 2007 17:26:51 -0700 From: Andrew Morton To: Dave Jones Cc: "Jeff V. Merkey" , Linux kernel , venki@gelk.kernelslacker.org Subject: Re: Preemption Broken: centrino_target busted under SMP on 2.6.20.4 Message-Id: <20070409172651.9bc619d6.akpm@linux-foundation.org> In-Reply-To: <20070405205034.GB3605@redhat.com> References: <46155CFF.70701@wolfmountaingroup.com> <20070405205034.GB3605@redhat.com> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.6; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 5 Apr 2007 16:50:34 -0400 Dave Jones wrote: > On Thu, Apr 05, 2007 at 02:33:03PM -0600, Jeff V. Merkey wrote: > > > > BUG: using smp_processor_id() in preemptible [00000001] code: > > kondemand/0/2473 > > caller is centrino_target+0xfb/0x600 > > [<401e3646>] debug_smp_processor_id+0x9e/0xb0 > > [<40112afb>] centrino_target+0xfb/0x600 > > [<40112a00>] centrino_target+0x0/0x600 > > [<40305bd9>] __cpufreq_driver_target+0x5c/0x6b > > [] do_dbs_timer+0x1bc/0x208 [cpufreq_ondemand] > > [<40134a46>] run_workqueue+0x85/0x125 > > [<40374f7f>] _spin_lock_irqsave+0x18/0x66 > > [] do_dbs_timer+0x0/0x208 [cpufreq_ondemand] > > [<401353fb>] worker_thread+0xf9/0x124 > > [<401213b9>] default_wake_function+0x0/0xc > > [<40135302>] worker_thread+0x0/0x124 > > [<40137b37>] kthread+0xb0/0xd9 > > [<40137a87>] kthread+0x0/0xd9 > > [<40104b2f>] kernel_thread_helper+0x7/0x10 > > Given speedstep-centrino is obsoleted in favour of acpi-cpufreq, > I'm reluctant to spend too much time turd-polishing. > This big-hammer diff should fix this.. > > Dave > > diff --git a/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c b/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c > index f43b987..824d0a2 100644 > --- a/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c > +++ b/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c > @@ -708,6 +708,7 @@ static int centrino_target (struct cpufreq_policy *policy, > saved_mask = current->cpus_allowed; > first_cpu = 1; > cpus_clear(covered_cpus); > + preempt_disable(); > for_each_cpu_mask(j, online_policy_cpus) { > /* > * Support for SMP systems. > @@ -798,6 +799,7 @@ static int centrino_target (struct cpufreq_policy *policy, > } > > migrate_end: > + preempt_enable(); > set_cpus_allowed(current, saved_mask); > return 0; > } This means we'll call set_cpus_allowed() while in atomic state, but set_cpus_allowed() does sleepy stuff.