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Commit 8def9060 authored by Viresh Kumar's avatar Viresh Kumar Committed by Ingo Molnar
Browse files

timer: Don't initialize 'tvec_base' on hotplug 



There is no need to call init_timers_cpu() on every CPU hotplug event,
there is not much we need to reset.

 - Timer-lists are already empty at the end of migrate_timers().
 - timer_jiffies will be refreshed while adding a new timer, after the
   CPU is online again.
 - active_timers and all_timers can be reset from migrate_timers().

Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/54a1c30ea7b805af55beb220cadf5a07a21b0a4d.1427814611.git.viresh.kumar@linaro.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent b337a938

kernel/time/timer.c

+43 −55
Original line number Diff line number Diff line
@@ -1543,43 +1543,6 @@ signed long __sched schedule_timeout_uninterruptible(signed long timeout) 
}

EXPORT_SYMBOL(schedule_timeout_uninterruptible);



static int init_timers_cpu(int cpu)

{

	struct tvec_base *base = per_cpu(tvec_bases, cpu);

	static char tvec_base_done[NR_CPUS];

	int j;



	if (!tvec_base_done[cpu]) {

		static char boot_cpu_skipped;



		if (!boot_cpu_skipped) {

			boot_cpu_skipped = 1; /* skip the boot cpu */

		} else {

			base = per_cpu_ptr(&__tvec_bases, cpu);

			per_cpu(tvec_bases, cpu) = base;

		}



		spin_lock_init(&base->lock);

		tvec_base_done[cpu] = 1;

		base->cpu = cpu;

	}



	for (j = 0; j < TVN_SIZE; j++) {

		INIT_LIST_HEAD(base->tv5.vec + j);

		INIT_LIST_HEAD(base->tv4.vec + j);

		INIT_LIST_HEAD(base->tv3.vec + j);

		INIT_LIST_HEAD(base->tv2.vec + j);

	}

	for (j = 0; j < TVR_SIZE; j++)

		INIT_LIST_HEAD(base->tv1.vec + j);



	base->timer_jiffies = jiffies;

	base->next_timer = base->timer_jiffies;

	base->active_timers = 0;

	base->all_timers = 0;

	return 0;

}



#ifdef CONFIG_HOTPLUG_CPU

static void migrate_timer_list(struct tvec_base *new_base, struct list_head *head)

{
@@ -1621,6 +1584,9 @@ static void migrate_timers(int cpu) 
		migrate_timer_list(new_base, old_base->tv5.vec + i);

	}



	old_base->active_timers = 0;

	old_base->all_timers = 0;



	spin_unlock(&old_base->lock);

	spin_unlock_irq(&new_base->lock);

	put_cpu_var(tvec_bases);
@@ -1630,25 +1596,16 @@ static void migrate_timers(int cpu) 
static int timer_cpu_notify(struct notifier_block *self,

				unsigned long action, void *hcpu)

{

	long cpu = (long)hcpu;

	int err;



	switch(action) {

	case CPU_UP_PREPARE:

	case CPU_UP_PREPARE_FROZEN:

		err = init_timers_cpu(cpu);

		if (err < 0)

			return notifier_from_errno(err);

		break;

#ifdef CONFIG_HOTPLUG_CPU

	switch (action) {

	case CPU_DEAD:

	case CPU_DEAD_FROZEN:

		migrate_timers(cpu);

		migrate_timers((long)hcpu);

		break;

#endif

	default:

		break;

	}

#endif

	return NOTIFY_OK;

}
@@ -1656,18 +1613,49 @@ static struct notifier_block timers_nb = { 
	.notifier_call	= timer_cpu_notify,

};



static void __init init_timer_cpu(struct tvec_base *base, int cpu)

{

	int j;



void __init init_timers(void)

	base->cpu = cpu;

	per_cpu(tvec_bases, cpu) = base;

	spin_lock_init(&base->lock);



	for (j = 0; j < TVN_SIZE; j++) {

		INIT_LIST_HEAD(base->tv5.vec + j);

		INIT_LIST_HEAD(base->tv4.vec + j);

		INIT_LIST_HEAD(base->tv3.vec + j);

		INIT_LIST_HEAD(base->tv2.vec + j);

	}

	for (j = 0; j < TVR_SIZE; j++)

		INIT_LIST_HEAD(base->tv1.vec + j);



	base->timer_jiffies = jiffies;

	base->next_timer = base->timer_jiffies;

}



static void __init init_timer_cpus(void)

{

	int err;

	struct tvec_base *base;

	int local_cpu = smp_processor_id();

	int cpu;



	for_each_possible_cpu(cpu) {

		if (cpu == local_cpu)

			base = &boot_tvec_bases;

		else

			base = per_cpu_ptr(&__tvec_bases, cpu);



		init_timer_cpu(base, cpu);

	}

}



void __init init_timers(void)

{

	/* ensure there are enough low bits for flags in timer->base pointer */

	BUILD_BUG_ON(__alignof__(struct tvec_base) & TIMER_FLAG_MASK);



	err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,

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

	BUG_ON(err != NOTIFY_OK);



	init_timer_cpus();

	init_timer_stats();

	register_cpu_notifier(&timers_nb);

	open_softirq(TIMER_SOFTIRQ, run_timer_softirq);