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Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull core timer changes from Ingo Molnar:
 "It contains continued generic-NOHZ work by Frederic and smaller
  cleanups."

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  time: Kill xtime_lock, replacing it with jiffies_lock
  clocksource: arm_generic: use this_cpu_ptr per-cpu helper
  clocksource: arm_generic: use integer math helpers
  time/jiffies: Make clocksource_jiffies static
  clocksource: clean up parse_pmtmr()
  tick: Correct the comments for tick_sched_timer()
  tick: Conditionally build nohz specific code in tick handler
  tick: Consolidate tick handling for high and low res handlers
  tick: Consolidate timekeeping handling code
This commit is contained in:
Linus Torvalds
2012-12-11 18:22:46 -08:00
parent f57d54bab6 9c3f9e2816
commit b64c5fda38
9 changed files with 84 additions and 106 deletions
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8
kernel/time/jiffies.c
View File

@@ -58,7 +58,7 @@ static cycle_t jiffies_read(struct clocksource *cs)
return (cycle_t) jiffies;
}
struct clocksource clocksource_jiffies = {
static struct clocksource clocksource_jiffies = {
.name = "jiffies",
.rating = 1, /* lowest valid rating*/
.read = jiffies_read,
@@ -67,6 +67,8 @@ struct clocksource clocksource_jiffies = {
.shift = JIFFIES_SHIFT,
};
__cacheline_aligned_in_smp DEFINE_SEQLOCK(jiffies_lock);
#if (BITS_PER_LONG < 64)
u64 get_jiffies_64(void)
{
@@ -74,9 +76,9 @@ u64 get_jiffies_64(void)
u64 ret;
do {
seq = read_seqbegin(&xtime_lock);
seq = read_seqbegin(&jiffies_lock);
ret = jiffies_64;
} while (read_seqretry(&xtime_lock, seq));
} while (read_seqretry(&jiffies_lock, seq));
return ret;
}
EXPORT_SYMBOL(get_jiffies_64);

8
kernel/time/tick-common.c
View File

@@ -63,13 +63,13 @@ int tick_is_oneshot_available(void)
static void tick_periodic(int cpu)
{
if (tick_do_timer_cpu == cpu) {
write_seqlock(&xtime_lock);
write_seqlock(&jiffies_lock);
/* Keep track of the next tick event */
tick_next_period = ktime_add(tick_next_period, tick_period);
do_timer(1);
write_sequnlock(&xtime_lock);
write_sequnlock(&jiffies_lock);
}
update_process_times(user_mode(get_irq_regs()));
@@ -130,9 +130,9 @@ void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
ktime_t next;
do {
seq = read_seqbegin(&xtime_lock);
seq = read_seqbegin(&jiffies_lock);
next = tick_next_period;
} while (read_seqretry(&xtime_lock, seq));
} while (read_seqretry(&jiffies_lock, seq));
clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);

1
kernel/time/tick-internal.h
View File

@@ -141,4 +141,3 @@ static inline int tick_device_is_functional(struct clock_event_device *dev)
#endif
extern void do_timer(unsigned long ticks);
extern seqlock_t xtime_lock;

131
kernel/time/tick-sched.c
View File

@@ -31,7 +31,7 @@
static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
/*
* The time, when the last jiffy update happened. Protected by xtime_lock.
* The time, when the last jiffy update happened. Protected by jiffies_lock.
*/
static ktime_t last_jiffies_update;
@@ -49,14 +49,14 @@ static void tick_do_update_jiffies64(ktime_t now)
ktime_t delta;
/*
* Do a quick check without holding xtime_lock:
* Do a quick check without holding jiffies_lock:
*/
delta = ktime_sub(now, last_jiffies_update);
if (delta.tv64 < tick_period.tv64)
return;
/* Reevalute with xtime_lock held */
write_seqlock(&xtime_lock);
/* Reevalute with jiffies_lock held */
write_seqlock(&jiffies_lock);
delta = ktime_sub(now, last_jiffies_update);
if (delta.tv64 >= tick_period.tv64) {
@@ -79,7 +79,7 @@ static void tick_do_update_jiffies64(ktime_t now)
/* Keep the tick_next_period variable up to date */
tick_next_period = ktime_add(last_jiffies_update, tick_period);
}
write_sequnlock(&xtime_lock);
write_sequnlock(&jiffies_lock);
}
/*
@@ -89,15 +89,58 @@ static ktime_t tick_init_jiffy_update(void)
{
ktime_t period;
write_seqlock(&xtime_lock);
write_seqlock(&jiffies_lock);
/* Did we start the jiffies update yet ? */
if (last_jiffies_update.tv64 == 0)
last_jiffies_update = tick_next_period;
period = last_jiffies_update;
write_sequnlock(&xtime_lock);
write_sequnlock(&jiffies_lock);
return period;
}
static void tick_sched_do_timer(ktime_t now)
{
int cpu = smp_processor_id();
#ifdef CONFIG_NO_HZ
/*
* Check if the do_timer duty was dropped. We don't care about
* concurrency: This happens only when the cpu in charge went
* into a long sleep. If two cpus happen to assign themself to
* this duty, then the jiffies update is still serialized by
* jiffies_lock.
*/
if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
tick_do_timer_cpu = cpu;
#endif
/* Check, if the jiffies need an update */
if (tick_do_timer_cpu == cpu)
tick_do_update_jiffies64(now);
}
static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
{
#ifdef CONFIG_NO_HZ
/*
* When we are idle and the tick is stopped, we have to touch
* the watchdog as we might not schedule for a really long
* time. This happens on complete idle SMP systems while
* waiting on the login prompt. We also increment the "start of
* idle" jiffy stamp so the idle accounting adjustment we do
* when we go busy again does not account too much ticks.
*/
if (ts->tick_stopped) {
touch_softlockup_watchdog();
if (is_idle_task(current))
ts->idle_jiffies++;
}
#endif
update_process_times(user_mode(regs));
profile_tick(CPU_PROFILING);
}
/*
* NOHZ - aka dynamic tick functionality
*/
@@ -282,11 +325,11 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
/* Read jiffies and the time when jiffies were updated last */
do {
seq = read_seqbegin(&xtime_lock);
seq = read_seqbegin(&jiffies_lock);
last_update = last_jiffies_update;
last_jiffies = jiffies;
time_delta = timekeeping_max_deferment();
} while (read_seqretry(&xtime_lock, seq));
} while (read_seqretry(&jiffies_lock, seq));
if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) || printk_needs_cpu(cpu) ||
arch_needs_cpu(cpu)) {
@@ -652,40 +695,12 @@ static void tick_nohz_handler(struct clock_event_device *dev)
{
struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
struct pt_regs *regs = get_irq_regs();
int cpu = smp_processor_id();
ktime_t now = ktime_get();
dev->next_event.tv64 = KTIME_MAX;
/*
* Check if the do_timer duty was dropped. We don't care about
* concurrency: This happens only when the cpu in charge went
* into a long sleep. If two cpus happen to assign themself to
* this duty, then the jiffies update is still serialized by
* xtime_lock.
*/
if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
tick_do_timer_cpu = cpu;
/* Check, if the jiffies need an update */
if (tick_do_timer_cpu == cpu)
tick_do_update_jiffies64(now);
/*
* When we are idle and the tick is stopped, we have to touch
* the watchdog as we might not schedule for a really long
* time. This happens on complete idle SMP systems while
* waiting on the login prompt. We also increment the "start
* of idle" jiffy stamp so the idle accounting adjustment we
* do when we go busy again does not account too much ticks.
*/
if (ts->tick_stopped) {
touch_softlockup_watchdog();
ts->idle_jiffies++;
}
update_process_times(user_mode(regs));
profile_tick(CPU_PROFILING);
tick_sched_do_timer(now);
tick_sched_handle(ts, regs);
while (tick_nohz_reprogram(ts, now)) {
now = ktime_get();
@@ -806,45 +821,15 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
container_of(timer, struct tick_sched, sched_timer);
struct pt_regs *regs = get_irq_regs();
ktime_t now = ktime_get();
int cpu = smp_processor_id();
#ifdef CONFIG_NO_HZ
/*
* Check if the do_timer duty was dropped. We don't care about
* concurrency: This happens only when the cpu in charge went
* into a long sleep. If two cpus happen to assign themself to
* this duty, then the jiffies update is still serialized by
* xtime_lock.
*/
if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
tick_do_timer_cpu = cpu;
#endif
/* Check, if the jiffies need an update */
if (tick_do_timer_cpu == cpu)
tick_do_update_jiffies64(now);
tick_sched_do_timer(now);
/*
* Do not call, when we are not in irq context and have
* no valid regs pointer
*/
if (regs) {
/*
* When we are idle and the tick is stopped, we have to touch
* the watchdog as we might not schedule for a really long
* time. This happens on complete idle SMP systems while
* waiting on the login prompt. We also increment the "start of
* idle" jiffy stamp so the idle accounting adjustment we do
* when we go busy again does not account too much ticks.
*/
if (ts->tick_stopped) {
touch_softlockup_watchdog();
if (is_idle_task(current))
ts->idle_jiffies++;
}
update_process_times(user_mode(regs));
profile_tick(CPU_PROFILING);
}
if (regs)
tick_sched_handle(ts, regs);
hrtimer_forward(timer, now, tick_period);
@@ -878,7 +863,7 @@ void tick_setup_sched_timer(void)
/* Get the next period (per cpu) */
hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
/* Offset the tick to avert xtime_lock contention. */
/* Offset the tick to avert jiffies_lock contention. */
if (sched_skew_tick) {
u64 offset = ktime_to_ns(tick_period) >> 1;
do_div(offset, num_possible_cpus());

14
kernel/time/timekeeping.c
View File

@@ -25,12 +25,6 @@
static struct timekeeper timekeeper;
/*
* This read-write spinlock protects us from races in SMP while
* playing with xtime.
*/
__cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
/* flag for if timekeeping is suspended */
int __read_mostly timekeeping_suspended;
@@ -1299,9 +1293,7 @@ struct timespec get_monotonic_coarse(void)
}
/*
* The 64-bit jiffies value is not atomic - you MUST NOT read it
* without sampling the sequence number in xtime_lock.
* jiffies is defined in the linker script...
* Must hold jiffies_lock
*/
void do_timer(unsigned long ticks)
{
@@ -1389,7 +1381,7 @@ EXPORT_SYMBOL_GPL(ktime_get_monotonic_offset);
*/
void xtime_update(unsigned long ticks)
{
write_seqlock(&xtime_lock);
write_seqlock(&jiffies_lock);
do_timer(ticks);
write_sequnlock(&xtime_lock);
write_sequnlock(&jiffies_lock);
}