Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936415Ab3DQSnc (ORCPT ); Wed, 17 Apr 2013 14:43:32 -0400 Received: from relay3.sgi.com ([192.48.152.1]:46414 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757572Ab3DQSn3 (ORCPT ); Wed, 17 Apr 2013 14:43:29 -0400 From: Robin Holt To: Ingo Molnar , "H. Peter Anvin" , "Srivatsa S. Bhat" , Russ Anderson Cc: Linux Kernel Mailing List , the arch/x86 maintainers Subject: [PATCH -v5 2/5] Migrate shutdown/reboot to boot cpu. Date: Wed, 17 Apr 2013 13:43:15 -0500 Message-Id: <1366224198-49485-3-git-send-email-holt@sgi.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1366224198-49485-1-git-send-email-holt@sgi.com> References: <1366224198-49485-1-git-send-email-holt@sgi.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3852 Lines: 117 We recently noticed that reboot of a 1024 cpu machine takes approx 16 minutes of just stopping the cpus. The slowdown was tracked to commit f96972f. The current implementation does all the work of hot removing the cpus before halting the system. We are switching to just migrating to the boot cpu and then continuing with shutdown/reboot. This also has the effect of not breaking x86's command line parameter for specifying the reboot cpu. Note, this code was shamelessly copied from arch/x86/kernel/reboot.c with bits removed pertaining to the reboot_cpu command line parameter. Signed-off-by: Robin Holt Tested-by: Shawn Guo To: Ingo Molnar To: Russ Anderson To: Oleg Nesterov Cc: Andrew Morton Cc: "H. Peter Anvin" Cc: Lai Jiangshan Cc: Linus Torvalds Cc: Linux Kernel Mailing List Cc: Michel Lespinasse Cc: Oleg Nesterov Cc: "Paul E. McKenney" Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Robin Holt Cc: "rusty@rustcorp.com.au" Cc: Tejun Heo Cc: the arch/x86 maintainers Cc: Thomas Gleixner Cc: --- Changes since -v4. - Integrated comments from Srivatsa S. Bhat - Used new cpu_hotplug_disable() function. - Added 'static' to new function. Changes since -v1. - Set PF_THREAD_BOUND before migrating to eliminate potential race. - Modified kernel_power_off to also migrate instead of using disable_nonboot_cpus(). --- kernel/sys.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/kernel/sys.c b/kernel/sys.c index 0da73cf..232214e 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -357,6 +357,24 @@ int unregister_reboot_notifier(struct notifier_block *nb) } EXPORT_SYMBOL(unregister_reboot_notifier); +static void migrate_to_reboot_cpu(void) +{ + /* The boot cpu is always logical cpu 0 */ + int reboot_cpu_id = 0; + + cpu_hotplug_disable(); + + /* Make certain the cpu I'm about to reboot on is online */ + if (!cpu_online(reboot_cpu_id)) + reboot_cpu_id = cpumask_first(cpu_online_mask); + + /* Prevent races with other tasks migrating this task */ + current->flags |= PF_THREAD_BOUND; + + /* Make certain I only run on the appropriate processor */ + set_cpus_allowed_ptr(current, cpumask_of(reboot_cpu_id)); +} + /** * kernel_restart - reboot the system * @cmd: pointer to buffer containing command to execute for restart @@ -368,7 +386,7 @@ EXPORT_SYMBOL(unregister_reboot_notifier); void kernel_restart(char *cmd) { kernel_restart_prepare(cmd); - disable_nonboot_cpus(); + migrate_to_reboot_cpu(); syscore_shutdown(); if (!cmd) printk(KERN_EMERG "Restarting system.\n"); @@ -395,7 +413,7 @@ static void kernel_shutdown_prepare(enum system_states state) void kernel_halt(void) { kernel_shutdown_prepare(SYSTEM_HALT); - disable_nonboot_cpus(); + migrate_to_reboot_cpu(); syscore_shutdown(); printk(KERN_EMERG "System halted.\n"); kmsg_dump(KMSG_DUMP_HALT); @@ -414,7 +432,7 @@ void kernel_power_off(void) kernel_shutdown_prepare(SYSTEM_POWER_OFF); if (pm_power_off_prepare) pm_power_off_prepare(); - disable_nonboot_cpus(); + migrate_to_reboot_cpu(); syscore_shutdown(); printk(KERN_EMERG "Power down.\n"); kmsg_dump(KMSG_DUMP_POWEROFF); -- 1.8.1.2 -- 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/