reboot: rigrate shutdown/reboot to boot cpu (cf7df378) · Commits · 戴 / test

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 ("kernel/sys.c: call disable_nonboot_cpus() in kernel_restart()"). 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 <holt@sgi.com> Tested-by:

Shawn Guo <shawn.guo@linaro.org> Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Russ Anderson <rja@sgi.com> Cc: Robin Holt <holt@sgi.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Cc: <stable@vger.kernel.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

kernel/sys.c

+26 −3

Original line number	Diff line number	Diff line
		@@ -362,6 +362,29 @@ int unregister_reboot_notifier(struct notifier_block *nb)
		}
		EXPORT_SYMBOL(unregister_reboot_notifier);

		/* Add backwards compatibility for stable trees. */
		#ifndef PF_NO_SETAFFINITY
		#define PF_NO_SETAFFINITY PF_THREAD_BOUND
		#endif

		static void migrate_to_reboot_cpu(void)
		{
		/* The boot cpu is always logical cpu 0 */
		int cpu = 0;

		cpu_hotplug_disable();

		/* Make certain the cpu I'm about to reboot on is online */
		if (!cpu_online(cpu))
		cpu = cpumask_first(cpu_online_mask);

		/* Prevent races with other tasks migrating this task */
		current->flags \|= PF_NO_SETAFFINITY;

		/* Make certain I only run on the appropriate processor */
		set_cpus_allowed_ptr(current, cpumask_of(cpu));
		}

		/**
		* kernel_restart - reboot the system
		* @cmd: pointer to buffer containing command to execute for restart
		@@ -373,7 +396,7 @@ 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");
		@@ -400,7 +423,7 @@ 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);
		@@ -419,7 +442,7 @@ 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);

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