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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: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Viresh Kumar 2015-03-31 20:49:01 +05:30 committed by Ingo Molnar
parent b337a9380f
commit 8def906044
1 changed files with 43 additions and 55 deletions
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98
kernel/time/timer.c
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@ -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;
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)
{
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)
{
int err;
/* 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);