From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756412Ab0HXWxn (ORCPT ); Tue, 24 Aug 2010 18:53:43 -0400 Received: from kroah.org ([198.145.64.141]:52078 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756352Ab0HXWxi (ORCPT ); Tue, 24 Aug 2010 18:53:38 -0400 X-Mailbox-Line: From gregkh@clark.site Tue Aug 24 15:25:23 2010 Message-Id: <20100824222523.535484685@clark.site> User-Agent: quilt/0.48-11.2 Date: Tue, 24 Aug 2010 15:24:25 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Borislav Petkov , "H. Peter Anvin" Subject: [13/59] x86, hotplug: Serialize CPU hotplug to avoid bringup concurrency issues In-Reply-To: <20100824224625.GA5449@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-stable review patch. If anyone has any objections, please let us know. ------------------ From: Borislav Petkov commit d7c53c9e822a4fefa13a0cae76f3190bfd0d5c11 upstream. When testing cpu hotplug code on 32-bit we kept hitting the "CPU%d: Stuck ??" message due to multiple cores concurrently accessing the cpu_callin_mask, among others. Since these codepaths are not protected from concurrent access due to the fact that there's no sane reason for making an already complex code unnecessarily more complex - we hit the issue only when insanely switching cores off- and online - serialize hotplugging cores on the sysfs level and be done with it. [ v2.1: fix !HOTPLUG_CPU build ] Signed-off-by: Borislav Petkov LKML-Reference: <20100819181029.GC17171@aftab> Signed-off-by: H. Peter Anvin Signed-off-by: Greg Kroah-Hartman --- arch/x86/Kconfig | 5 +++++ arch/x86/kernel/smpboot.c | 19 +++++++++++++++++++ 2 files changed, 24 insertions(+) --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -227,6 +227,11 @@ config X86_32_LAZY_GS config KTIME_SCALAR def_bool X86_32 + +config ARCH_CPU_PROBE_RELEASE + def_bool y + depends on HOTPLUG_CPU + source "init/Kconfig" source "kernel/Kconfig.freezer" --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -88,6 +88,25 @@ DEFINE_PER_CPU(int, cpu_state) = { 0 }; static DEFINE_PER_CPU(struct task_struct *, idle_thread_array); #define get_idle_for_cpu(x) (per_cpu(idle_thread_array, x)) #define set_idle_for_cpu(x, p) (per_cpu(idle_thread_array, x) = (p)) + +/* + * We need this for trampoline_base protection from concurrent accesses when + * off- and onlining cores wildly. + */ +static DEFINE_MUTEX(x86_cpu_hotplug_driver_mutex); + +void cpu_hotplug_driver_lock() +{ + mutex_lock(&x86_cpu_hotplug_driver_mutex); +} + +void cpu_hotplug_driver_unlock() +{ + mutex_unlock(&x86_cpu_hotplug_driver_mutex); +} + +ssize_t arch_cpu_probe(const char *buf, size_t count) { return -1; } +ssize_t arch_cpu_release(const char *buf, size_t count) { return -1; } #else static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ; #define get_idle_for_cpu(x) (idle_thread_array[(x)])