Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753130AbYHKMa5 (ORCPT ); Mon, 11 Aug 2008 08:30:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751498AbYHKMau (ORCPT ); Mon, 11 Aug 2008 08:30:50 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:55481 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751316AbYHKMat (ORCPT ); Mon, 11 Aug 2008 08:30:49 -0400 Date: Mon, 11 Aug 2008 14:30:20 +0200 From: Ingo Molnar To: Dmitry Adamushko Cc: "Rafael J. Wysocki" , "Langsdorf, Mark" , lkml , Gautham R Shenoy , Peter Zijlstra , Andrew Morton , Linus Torvalds Subject: Re: Regression in 2.6.27-rc1 for set_cpus_allowed_ptr Message-ID: <20080811123020.GB10082@elte.hu> References: <6453C3CB8E2B3646B0D020C112613273C5AC5A@sausexmb4.amd.com> <200808082303.41068.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3663 Lines: 120 * Dmitry Adamushko wrote: > 2008/8/8 Rafael J. Wysocki : > > [Adding CCs] > > > > On Friday, 8 of August 2008, Langsdorf, Mark wrote: > >> One of my co-workers noticed that the powernow-k8 > >> driver no longer restarts when a CPU core is > >> hot-disabled and then hot-enabled on AMD quad-core > >> systems. > >> > >> The following comands work fine on 2.6.26 and fail > >> on 2.6.27-rc1: > >> > >> echo 0 > /sys/devices/system/cpu/cpu3/online > >> echo 1 > /sys/devices/system/cpu/cpu3/online > >> find /sys -name cpufreq > >> > >> For 2.6.26, the find will return a cpufreq > >> directory for each processor. In 2.6.27-rc1, > >> the cpu3 directory is missing. > >> > >> After digging through the code, the following > >> logic is failing when the core is hot-enabled > >> at runtime. The code works during the boot > >> sequence. > >> > >> cpumask_t = current->cpus_allowed; > >> set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu)); > >> if (smp_processor_id() != cpu) > >> return -ENODEV; > >> > > > if it gets called from any of the cpu-hotplug handlers, it won't work > now (x86-microcode is another victim). > > Please give a try to the following patch: http://lkml.org/lkml/2008/7/30/171 > > does it help? > > (the explanation is also available in this thread). i've queued up the fix below in tip/sched/urgent. Ingo ------------------------> >From 3bc8fb8f85b79aa2d6341adb5090799b93d64bc9 Mon Sep 17 00:00:00 2001 From: Dmitry Adamushko Date: Wed, 30 Jul 2008 12:34:04 +0200 Subject: [PATCH] sched, cpu hotplug: fix set_cpus_allowed() use in hotplug callbacks Mark Langsdorf reported: > One of my co-workers noticed that the powernow-k8 > driver no longer restarts when a CPU core is > hot-disabled and then hot-enabled on AMD quad-core > systems. > > The following comands work fine on 2.6.26 and fail > on 2.6.27-rc1: > > echo 0 > /sys/devices/system/cpu/cpu3/online > echo 1 > /sys/devices/system/cpu/cpu3/online > find /sys -name cpufreq > > For 2.6.26, the find will return a cpufreq > directory for each processor. In 2.6.27-rc1, > the cpu3 directory is missing. > > After digging through the code, the following > logic is failing when the core is hot-enabled > at runtime. The code works during the boot > sequence. > > cpumask_t = current->cpus_allowed; > set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu)); > if (smp_processor_id() != cpu) > return -ENODEV; a similar problem also affects the microcode driver. So set the CPU active before calling the CPU_ONLINE notifier chain, there are a handful of notifiers that use set_cpus_allowed(). Signed-off-by: Ingo Molnar --- kernel/cpu.c | 5 ++--- 1 files changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index e202a68..c977c33 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -349,6 +349,8 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) goto out_notify; BUG_ON(!cpu_online(cpu)); + cpu_set(cpu, cpu_active_map); + /* Now call notifier in preparation. */ raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu); @@ -383,9 +385,6 @@ int __cpuinit cpu_up(unsigned int cpu) err = _cpu_up(cpu, 0); - if (cpu_online(cpu)) - cpu_set(cpu, cpu_active_map); - out: cpu_maps_update_done(); return err; -- 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/