Commit 0441a559 authored by Qais Yousef's avatar Qais Yousef Committed by Thomas Gleixner
Browse files

cpu/hotplug: Create a new function to shutdown nonboot cpus 



This function will be used later in machine_shutdown() for some
architectures.

disable_nonboot_cpus() is not safe to use when doing machine_down(),
because it relies on freeze_secondary_cpus() which in turn is a
suspend/resume related freeze and could abort if the logic detects any
pending activities that can prevent finishing the offlining process.

Signed-off-by: default avatarQais Yousef <qais.yousef@arm.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200323135110.30522-3-qais.yousef@arm.com
parent 93ef1429

include/linux/cpu.h

+2 −0
Original line number Diff line number Diff line
@@ -120,6 +120,7 @@ extern void cpu_hotplug_enable(void); 
void clear_tasks_mm_cpumask(int cpu);

int cpu_down(unsigned int cpu);

int remove_cpu(unsigned int cpu);

extern void smp_shutdown_nonboot_cpus(unsigned int primary_cpu);



#else /* CONFIG_HOTPLUG_CPU */
@@ -131,6 +132,7 @@ static inline int cpus_read_trylock(void) { return true; } 
static inline void lockdep_assert_cpus_held(void) { }

static inline void cpu_hotplug_disable(void) { }

static inline void cpu_hotplug_enable(void) { }

static inline void smp_shutdown_nonboot_cpus(unsigned int primary_cpu) { }

#endif	/* !CONFIG_HOTPLUG_CPU */



/* Wrappers which go away once all code is converted */

kernel/cpu.c

+42 −0
Original line number Diff line number Diff line
@@ -1069,6 +1069,48 @@ int remove_cpu(unsigned int cpu) 
}

EXPORT_SYMBOL_GPL(remove_cpu);



void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)

{

	unsigned int cpu;

	int error;



	cpu_maps_update_begin();



	/*

	 * Make certain the cpu I'm about to reboot on is online.

	 *

	 * This is inline to what migrate_to_reboot_cpu() already do.

	 */

	if (!cpu_online(primary_cpu))

		primary_cpu = cpumask_first(cpu_online_mask);



	for_each_online_cpu(cpu) {

		if (cpu == primary_cpu)

			continue;



		error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);

		if (error) {

			pr_err("Failed to offline CPU%d - error=%d",

				cpu, error);

			break;

		}

	}



	/*

	 * Ensure all but the reboot CPU are offline.

	 */

	BUG_ON(num_online_cpus() > 1);



	/*

	 * Make sure the CPUs won't be enabled by someone else after this

	 * point. Kexec will reboot to a new kernel shortly resetting

	 * everything along the way.

	 */

	cpu_hotplug_disabled++;



	cpu_maps_update_done();

}



#else

#define takedown_cpu		NULL

#endif /*CONFIG_HOTPLUG_CPU*/

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