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Commit 9a7a71b1 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by John Stultz
Browse files

timekeeping: Split timekeeper_lock into lock and seqcount 



We want to shorten the seqcount write hold time. So split the seqlock
into a lock and a seqcount.

Open code the seqwrite_lock in the places which matter and drop the
sequence counter update where it's pointless.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
[jstultz: Merge fixups from CLOCK_TAI collisions]
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent 7e40672d

kernel/time/timekeeping.c

+73 −59
Original line number Diff line number Diff line
@@ -26,7 +26,8 @@ 
#include "tick-internal.h"



static struct timekeeper timekeeper;

static DEFINE_SEQLOCK(timekeeper_lock);

static DEFINE_RAW_SPINLOCK(timekeeper_lock);

static seqcount_t timekeeper_seq;



/* flag for if timekeeping is suspended */

int __read_mostly timekeeping_suspended;
@@ -204,8 +205,6 @@ static void update_pvclock_gtod(struct timekeeper *tk) 


/**

 * pvclock_gtod_register_notifier - register a pvclock timedata update listener

 *

 * Must hold write on timekeeper.lock

 */

int pvclock_gtod_register_notifier(struct notifier_block *nb)

{
@@ -213,11 +212,10 @@ int pvclock_gtod_register_notifier(struct notifier_block *nb) 
	unsigned long flags;

	int ret;



	write_seqlock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);

	/* update timekeeping data */

	update_pvclock_gtod(tk);

	write_sequnlock_irqrestore(&timekeeper_lock, flags);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);



	return ret;

}
@@ -226,23 +224,21 @@ EXPORT_SYMBOL_GPL(pvclock_gtod_register_notifier); 
/**

 * pvclock_gtod_unregister_notifier - unregister a pvclock

 * timedata update listener

 *

 * Must hold write on timekeeper.lock

 */

int pvclock_gtod_unregister_notifier(struct notifier_block *nb)

{

	unsigned long flags;

	int ret;



	write_seqlock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	ret = raw_notifier_chain_unregister(&pvclock_gtod_chain, nb);

	write_sequnlock_irqrestore(&timekeeper_lock, flags);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);



	return ret;

}

EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);



/* must hold write on timekeeper.lock */

/* must hold timekeeper_lock */

static void timekeeping_update(struct timekeeper *tk, bool clearntp)

{

	if (clearntp) {
@@ -296,12 +292,12 @@ int __getnstimeofday(struct timespec *ts) 
	s64 nsecs = 0;



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);



		ts->tv_sec = tk->xtime_sec;

		nsecs = timekeeping_get_ns(tk);



	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	ts->tv_nsec = 0;

	timespec_add_ns(ts, nsecs);
@@ -337,11 +333,11 @@ ktime_t ktime_get(void) 
	WARN_ON(timekeeping_suspended);



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);

		secs = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;

		nsecs = timekeeping_get_ns(tk) + tk->wall_to_monotonic.tv_nsec;



	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));

	/*

	 * Use ktime_set/ktime_add_ns to create a proper ktime on

	 * 32-bit architectures without CONFIG_KTIME_SCALAR.
@@ -368,12 +364,12 @@ void ktime_get_ts(struct timespec *ts) 
	WARN_ON(timekeeping_suspended);



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);

		ts->tv_sec = tk->xtime_sec;

		nsec = timekeeping_get_ns(tk);

		tomono = tk->wall_to_monotonic;



	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	ts->tv_sec += tomono.tv_sec;

	ts->tv_nsec = 0;
@@ -397,12 +393,12 @@ void timekeeping_clocktai(struct timespec *ts) 
	WARN_ON(timekeeping_suspended);



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);



		ts->tv_sec = tk->xtime_sec + tk->tai_offset;

		nsecs = timekeeping_get_ns(tk);



	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	ts->tv_nsec = 0;

	timespec_add_ns(ts, nsecs);
@@ -445,7 +441,7 @@ void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real) 
	WARN_ON_ONCE(timekeeping_suspended);



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);



		*ts_raw = tk->raw_time;

		ts_real->tv_sec = tk->xtime_sec;
@@ -454,7 +450,7 @@ void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real) 
		nsecs_raw = timekeeping_get_ns_raw(tk);

		nsecs_real = timekeeping_get_ns(tk);



	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	timespec_add_ns(ts_raw, nsecs_raw);

	timespec_add_ns(ts_real, nsecs_real);
@@ -494,7 +490,8 @@ int do_settimeofday(const struct timespec *tv) 
	if (!timespec_valid_strict(tv))

		return -EINVAL;



	write_seqlock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&timekeeper_seq);



	timekeeping_forward_now(tk);
@@ -508,7 +505,8 @@ int do_settimeofday(const struct timespec *tv) 


	timekeeping_update(tk, true);



	write_sequnlock_irqrestore(&timekeeper_lock, flags);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);



	/* signal hrtimers about time change */

	clock_was_set();
@@ -533,7 +531,8 @@ int timekeeping_inject_offset(struct timespec *ts) 
	if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)

		return -EINVAL;



	write_seqlock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&timekeeper_seq);



	timekeeping_forward_now(tk);
@@ -550,7 +549,8 @@ int timekeeping_inject_offset(struct timespec *ts) 
error: /* even if we error out, we forwarded the time, so call update */

	timekeeping_update(tk, true);



	write_sequnlock_irqrestore(&timekeeper_lock, flags);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);



	/* signal hrtimers about time change */

	clock_was_set();
@@ -571,9 +571,9 @@ s32 timekeeping_get_tai_offset(void) 
	s32 ret;



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);

		ret = tk->tai_offset;

	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	return ret;

}
@@ -597,9 +597,11 @@ void timekeeping_set_tai_offset(s32 tai_offset) 
	struct timekeeper *tk = &timekeeper;

	unsigned long flags;



	write_seqlock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&timekeeper_seq);

	__timekeeping_set_tai_offset(tk, tai_offset);

	write_sequnlock_irqrestore(&timekeeper_lock, flags);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

}



/**
@@ -615,7 +617,8 @@ static int change_clocksource(void *data) 


	new = (struct clocksource *) data;



	write_seqlock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&timekeeper_seq);



	timekeeping_forward_now(tk);

	if (!new->enable || new->enable(new) == 0) {
@@ -626,7 +629,8 @@ static int change_clocksource(void *data) 
	}

	timekeeping_update(tk, true);



	write_sequnlock_irqrestore(&timekeeper_lock, flags);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);



	return 0;

}
@@ -676,11 +680,11 @@ void getrawmonotonic(struct timespec *ts) 
	s64 nsecs;



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);

		nsecs = timekeeping_get_ns_raw(tk);

		*ts = tk->raw_time;



	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	timespec_add_ns(ts, nsecs);

}
@@ -696,11 +700,11 @@ int timekeeping_valid_for_hres(void) 
	int ret;



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);



		ret = tk->clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;



	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	return ret;

}
@@ -715,11 +719,11 @@ u64 timekeeping_max_deferment(void) 
	u64 ret;



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);



		ret = tk->clock->max_idle_ns;



	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	return ret;

}
@@ -784,7 +788,8 @@ void __init timekeeping_init(void) 


	ntp_init();



	write_seqlock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&timekeeper_seq);

	clock = clocksource_default_clock();

	if (clock->enable)

		clock->enable(clock);
@@ -803,7 +808,8 @@ void __init timekeeping_init(void) 
	tmp.tv_nsec = 0;

	tk_set_sleep_time(tk, tmp);



	write_sequnlock_irqrestore(&timekeeper_lock, flags);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

}



/* time in seconds when suspend began */
@@ -851,7 +857,8 @@ void timekeeping_inject_sleeptime(struct timespec *delta) 
	if (has_persistent_clock())

		return;



	write_seqlock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&timekeeper_seq);



	timekeeping_forward_now(tk);
@@ -859,7 +866,8 @@ void timekeeping_inject_sleeptime(struct timespec *delta) 


	timekeeping_update(tk, true);



	write_sequnlock_irqrestore(&timekeeper_lock, flags);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);



	/* signal hrtimers about time change */

	clock_was_set();
@@ -886,7 +894,8 @@ static void timekeeping_resume(void) 
	clockevents_resume();

	clocksource_resume();



	write_seqlock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&timekeeper_seq);



	/*

	 * After system resumes, we need to calculate the suspended time and
@@ -938,7 +947,8 @@ static void timekeeping_resume(void) 
	tk->ntp_error = 0;

	timekeeping_suspended = 0;

	timekeeping_update(tk, false);

	write_sequnlock_irqrestore(&timekeeper_lock, flags);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);



	touch_softlockup_watchdog();
@@ -957,7 +967,8 @@ static int timekeeping_suspend(void) 


	read_persistent_clock(&timekeeping_suspend_time);



	write_seqlock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&timekeeper_seq);

	timekeeping_forward_now(tk);

	timekeeping_suspended = 1;
@@ -980,7 +991,8 @@ static int timekeeping_suspend(void) 
		timekeeping_suspend_time =

			timespec_add(timekeeping_suspend_time, delta_delta);

	}

	write_sequnlock_irqrestore(&timekeeper_lock, flags);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);



	clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);

	clocksource_suspend();
@@ -1320,7 +1332,8 @@ static void update_wall_time(void) 
	int shift = 0, maxshift;

	unsigned long flags;



	write_seqlock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&timekeeper_seq);



	/* Make sure we're fully resumed: */

	if (unlikely(timekeeping_suspended))
@@ -1375,7 +1388,8 @@ static void update_wall_time(void) 
	timekeeping_update(tk, false);



out:

	write_sequnlock_irqrestore(&timekeeper_lock, flags);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);



}
@@ -1423,13 +1437,13 @@ void get_monotonic_boottime(struct timespec *ts) 
	WARN_ON(timekeeping_suspended);



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);

		ts->tv_sec = tk->xtime_sec;

		nsec = timekeeping_get_ns(tk);

		tomono = tk->wall_to_monotonic;

		sleep = tk->total_sleep_time;



	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	ts->tv_sec += tomono.tv_sec + sleep.tv_sec;

	ts->tv_nsec = 0;
@@ -1488,10 +1502,10 @@ struct timespec current_kernel_time(void) 
	unsigned long seq;



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);



		now = tk_xtime(tk);

	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	return now;

}
@@ -1504,11 +1518,11 @@ struct timespec get_monotonic_coarse(void) 
	unsigned long seq;



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);



		now = tk_xtime(tk);

		mono = tk->wall_to_monotonic;

	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	set_normalized_timespec(&now, now.tv_sec + mono.tv_sec,

				now.tv_nsec + mono.tv_nsec);
@@ -1539,11 +1553,11 @@ void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim, 
	unsigned long seq;



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);

		*xtim = tk_xtime(tk);

		*wtom = tk->wall_to_monotonic;

		*sleep = tk->total_sleep_time;

	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));

}



#ifdef CONFIG_HIGH_RES_TIMERS
@@ -1564,7 +1578,7 @@ ktime_t ktime_get_update_offsets(ktime_t *offs_real, ktime_t *offs_boot, 
	u64 secs, nsecs;



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);



		secs = tk->xtime_sec;

		nsecs = timekeeping_get_ns(tk);
@@ -1572,7 +1586,7 @@ ktime_t ktime_get_update_offsets(ktime_t *offs_real, ktime_t *offs_boot, 
		*offs_real = tk->offs_real;

		*offs_boot = tk->offs_boot;

		*offs_tai = tk->offs_tai;

	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	now = ktime_add_ns(ktime_set(secs, 0), nsecs);

	now = ktime_sub(now, *offs_real);
@@ -1590,9 +1604,9 @@ ktime_t ktime_get_monotonic_offset(void) 
	struct timespec wtom;



	do {

		seq = read_seqbegin(&timekeeper_lock);

		seq = read_seqcount_begin(&timekeeper_seq);

		wtom = tk->wall_to_monotonic;

	} while (read_seqretry(&timekeeper_lock, seq));

	} while (read_seqcount_retry(&timekeeper_seq, seq));



	return timespec_to_ktime(wtom);

}