time: Kill xtime_lock, replacing it with jiffies_lock

Now that timekeeping is protected by its own locks, rename
the xtime_lock to jifffies_lock to better describe what it
protects.

CC: Thomas Gleixner <tglx@linutronix.de>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
This commit is contained in:
John Stultz 2012-02-28 16:50:11 -08:00
parent 47c8c91b2d
commit d6ad418763
7 changed files with 25 additions and 31 deletions

View File

@ -35,7 +35,7 @@ static cycle_t i8253_read(struct clocksource *cs)
raw_spin_lock_irqsave(&i8253_lock, flags);
/*
* Although our caller may have the read side of xtime_lock,
* Although our caller may have the read side of jiffies_lock,
* this is now a seqlock, and we are cheating in this routine
* by having side effects on state that we cannot undo if
* there is a collision on the seqlock and our caller has to

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@ -70,11 +70,12 @@ extern int register_refined_jiffies(long clock_tick_rate);
/*
* The 64-bit value is not atomic - you MUST NOT read it
* without sampling the sequence number in xtime_lock.
* without sampling the sequence number in jiffies_lock.
* get_jiffies_64() will do this for you as appropriate.
*/
extern u64 __jiffy_data jiffies_64;
extern unsigned long volatile __jiffy_data jiffies;
extern seqlock_t jiffies_lock;
#if (BITS_PER_LONG < 64)
u64 get_jiffies_64(void);

View File

@ -67,6 +67,8 @@ static 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);

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@ -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);

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@ -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;

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);
}
/*
@ -89,12 +89,12 @@ 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;
}
@ -282,11 +282,11 @@ 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)) {
@ -658,7 +658,7 @@ static void tick_nohz_handler(struct clock_event_device *dev)
* 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.
* jiffies_lock.
*/
if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
tick_do_timer_cpu = cpu;
@ -810,7 +810,7 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
* 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.
* jiffies_lock.
*/
if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
tick_do_timer_cpu = cpu;

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@ -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);
}