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Commit e69aab13 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

cpu/hotplug: Make wait for dead cpu completion based 



Kill the busy spinning on the control side and just wait for the hotplugged
cpu to tell that it reached the dead state.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.776157858@linutronix.de


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 8df3e07e

include/linux/cpu.h

+3 −2
Original line number Original line Diff line number Diff line
@@ -276,14 +276,15 @@ void arch_cpu_idle_enter(void); 
void arch_cpu_idle_exit(void);

void arch_cpu_idle_exit(void);

void arch_cpu_idle_dead(void);

void arch_cpu_idle_dead(void);





DECLARE_PER_CPU(bool, cpu_dead_idle);



int cpu_report_state(int cpu);

int cpu_report_state(int cpu);

int cpu_check_up_prepare(int cpu);

int cpu_check_up_prepare(int cpu);

void cpu_set_state_online(int cpu);

void cpu_set_state_online(int cpu);

#ifdef CONFIG_HOTPLUG_CPU

#ifdef CONFIG_HOTPLUG_CPU

bool cpu_wait_death(unsigned int cpu, int seconds);

bool cpu_wait_death(unsigned int cpu, int seconds);

bool cpu_report_death(void);

bool cpu_report_death(void);

void cpuhp_report_idle_dead(void);

#else

static inline void cpuhp_report_idle_dead(void) { }

#endif /* #ifdef CONFIG_HOTPLUG_CPU */

#endif /* #ifdef CONFIG_HOTPLUG_CPU */





#endif /* _LINUX_CPU_H_ */
 
#endif /* _LINUX_CPU_H_ */

include/linux/cpuhotplug.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -6,6 +6,7 @@ enum cpuhp_state { 
	CPUHP_CREATE_THREADS,

	CPUHP_CREATE_THREADS,

	CPUHP_NOTIFY_PREPARE,

	CPUHP_NOTIFY_PREPARE,

	CPUHP_BRINGUP_CPU,

	CPUHP_BRINGUP_CPU,

	CPUHP_AP_IDLE_DEAD,

	CPUHP_AP_OFFLINE,

	CPUHP_AP_OFFLINE,

	CPUHP_AP_NOTIFY_STARTING,

	CPUHP_AP_NOTIFY_STARTING,

	CPUHP_AP_ONLINE,

	CPUHP_AP_ONLINE,

kernel/cpu.c

+12 −4
Original line number Original line Diff line number Diff line
@@ -688,6 +688,7 @@ static int take_cpu_down(void *_param) 




static int takedown_cpu(unsigned int cpu)

static int takedown_cpu(unsigned int cpu)

{

{

	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);

	int err;

	int err;





	/*

	/*
@@ -733,10 +734,8 @@ static int takedown_cpu(unsigned int cpu) 
	 *

	 *

	 * Wait for the stop thread to go away.

	 * Wait for the stop thread to go away.

	 */

	 */

	while (!per_cpu(cpu_dead_idle, cpu))

	wait_for_completion(&st->done);

		cpu_relax();

	BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);

	smp_mb(); /* Read from cpu_dead_idle before __cpu_die(). */

	per_cpu(cpu_dead_idle, cpu) = false;





	/* Interrupts are moved away from the dying cpu, reenable alloc/free */

	/* Interrupts are moved away from the dying cpu, reenable alloc/free */

	irq_unlock_sparse();

	irq_unlock_sparse();
@@ -756,6 +755,15 @@ static int notify_dead(unsigned int cpu) 
	return 0;

	return 0;

}

}





void cpuhp_report_idle_dead(void)

{

	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);



	BUG_ON(st->state != CPUHP_AP_OFFLINE);

	st->state = CPUHP_AP_IDLE_DEAD;

	complete(&st->done);

}



#else

#else

#define notify_down_prepare	NULL

#define notify_down_prepare	NULL

#define takedown_cpu		NULL

#define takedown_cpu		NULL

kernel/sched/idle.c

+1 −4
Original line number Original line Diff line number Diff line
@@ -194,8 +194,6 @@ static void cpuidle_idle_call(void) 
	rcu_idle_exit();

	rcu_idle_exit();

}

}





DEFINE_PER_CPU(bool, cpu_dead_idle);



/*

/*

 * Generic idle loop implementation

 * Generic idle loop implementation

 *

 *
@@ -224,8 +222,7 @@ static void cpu_idle_loop(void) 
			if (cpu_is_offline(smp_processor_id())) {

			if (cpu_is_offline(smp_processor_id())) {

				rcu_cpu_notify(NULL, CPU_DYING_IDLE,

				rcu_cpu_notify(NULL, CPU_DYING_IDLE,

					       (void *)(long)smp_processor_id());

					       (void *)(long)smp_processor_id());

				smp_mb(); /* all activity before dead. */

				cpuhp_report_idle_dead();

				this_cpu_write(cpu_dead_idle, true);

				arch_cpu_idle_dead();

				arch_cpu_idle_dead();

			}

			}