Commit 780427f0 authored by David Vrabel's avatar David Vrabel Committed by Thomas Gleixner
Browse files

timekeeping: Indicate that clock was set in the pvclock gtod notifier 



If the clock was set (stepped), set the action parameter to functions
in the pvclock gtod notifier chain to non-zero.  This allows the
callee to only do work if the clock was stepped.

This will be used on Xen as the synchronization of the Xen wallclock
to the control domain's (dom0) system time will be done with this
notifier and updating on every timer tick is unnecessary and too
expensive.

Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: <xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/1372329348-20841-4-git-send-email-david.vrabel@citrix.com


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 04397fe9

include/linux/pvclock_gtod.h

+7 −0
Original line number Original line Diff line number Diff line
@@ -3,6 +3,13 @@ 




#include <linux/notifier.h>

#include <linux/notifier.h>





/*

 * The pvclock gtod notifier is called when the system time is updated

 * and is used to keep guest time synchronized with host time.

 *

 * The 'action' parameter in the notifier function is false (0), or

 * true (non-zero) if system time was stepped.

 */

extern int pvclock_gtod_register_notifier(struct notifier_block *nb);

extern int pvclock_gtod_register_notifier(struct notifier_block *nb);

extern int pvclock_gtod_unregister_notifier(struct notifier_block *nb);

extern int pvclock_gtod_unregister_notifier(struct notifier_block *nb);

kernel/time/timekeeping.c

+18 −12
Original line number Original line Diff line number Diff line
@@ -29,6 +29,7 @@ 




#define TK_CLEAR_NTP		(1 << 0)

#define TK_CLEAR_NTP		(1 << 0)

#define TK_MIRROR		(1 << 1)

#define TK_MIRROR		(1 << 1)

#define TK_CLOCK_WAS_SET	(1 << 2)





static struct timekeeper timekeeper;

static struct timekeeper timekeeper;

static DEFINE_RAW_SPINLOCK(timekeeper_lock);

static DEFINE_RAW_SPINLOCK(timekeeper_lock);
@@ -204,9 +205,9 @@ static inline s64 timekeeping_get_ns_raw(struct timekeeper *tk) 




static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);

static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);





static void update_pvclock_gtod(struct timekeeper *tk)

static void update_pvclock_gtod(struct timekeeper *tk, bool was_set)

{

{

	raw_notifier_call_chain(&pvclock_gtod_chain, 0, tk);

	raw_notifier_call_chain(&pvclock_gtod_chain, was_set, tk);

}

}





/**

/**
@@ -220,7 +221,7 @@ int pvclock_gtod_register_notifier(struct notifier_block *nb) 




	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);

	ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);

	update_pvclock_gtod(tk);

	update_pvclock_gtod(tk, true);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);





	return ret;

	return ret;
@@ -252,7 +253,7 @@ static void timekeeping_update(struct timekeeper *tk, unsigned int action) 
		ntp_clear();

		ntp_clear();

	}

	}

	update_vsyscall(tk);

	update_vsyscall(tk);

	update_pvclock_gtod(tk);

	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);





	if (action & TK_MIRROR)

	if (action & TK_MIRROR)

		memcpy(&shadow_timekeeper, &timekeeper, sizeof(timekeeper));

		memcpy(&shadow_timekeeper, &timekeeper, sizeof(timekeeper));
@@ -512,7 +513,7 @@ int do_settimeofday(const struct timespec *tv) 




	tk_set_xtime(tk, tv);

	tk_set_xtime(tk, tv);





	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR);

	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);





	write_seqcount_end(&timekeeper_seq);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
@@ -556,7 +557,7 @@ int timekeeping_inject_offset(struct timespec *ts) 
	tk_set_wall_to_mono(tk, timespec_sub(tk->wall_to_monotonic, *ts));

	tk_set_wall_to_mono(tk, timespec_sub(tk->wall_to_monotonic, *ts));





error: /* even if we error out, we forwarded the time, so call update */

error: /* even if we error out, we forwarded the time, so call update */

	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR);

	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);





	write_seqcount_end(&timekeeper_seq);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
@@ -646,7 +647,7 @@ static int change_clocksource(void *data) 
			module_put(new->owner);

			module_put(new->owner);

		}

		}

	}

	}

	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR);

	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);





	write_seqcount_end(&timekeeper_seq);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
@@ -887,7 +888,7 @@ void timekeeping_inject_sleeptime(struct timespec *delta) 




	__timekeeping_inject_sleeptime(tk, delta);

	__timekeeping_inject_sleeptime(tk, delta);





	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR);

	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);





	write_seqcount_end(&timekeeper_seq);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
@@ -969,7 +970,7 @@ static void timekeeping_resume(void) 
	tk->cycle_last = clock->cycle_last = cycle_now;

	tk->cycle_last = clock->cycle_last = cycle_now;

	tk->ntp_error = 0;

	tk->ntp_error = 0;

	timekeeping_suspended = 0;

	timekeeping_suspended = 0;

	timekeeping_update(tk, TK_MIRROR);

	timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);

	write_seqcount_end(&timekeeper_seq);

	write_seqcount_end(&timekeeper_seq);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
@@ -1243,9 +1244,10 @@ out_adjust: 
 * It also calls into the NTP code to handle leapsecond processing.

 * It also calls into the NTP code to handle leapsecond processing.

 *

 *

 */

 */

static inline void accumulate_nsecs_to_secs(struct timekeeper *tk)

static inline unsigned int accumulate_nsecs_to_secs(struct timekeeper *tk)

{

{

	u64 nsecps = (u64)NSEC_PER_SEC << tk->shift;

	u64 nsecps = (u64)NSEC_PER_SEC << tk->shift;

	unsigned int action = 0;





	while (tk->xtime_nsec >= nsecps) {

	while (tk->xtime_nsec >= nsecps) {

		int leap;

		int leap;
@@ -1268,8 +1270,10 @@ static inline void accumulate_nsecs_to_secs(struct timekeeper *tk) 
			__timekeeping_set_tai_offset(tk, tk->tai_offset - leap);

			__timekeeping_set_tai_offset(tk, tk->tai_offset - leap);





			clock_was_set_delayed();

			clock_was_set_delayed();

			action = TK_CLOCK_WAS_SET;

		}

		}

	}

	}

	return action;

}

}





/**

/**
@@ -1354,6 +1358,7 @@ static void update_wall_time(void) 
	struct timekeeper *tk = &shadow_timekeeper;

	struct timekeeper *tk = &shadow_timekeeper;

	cycle_t offset;

	cycle_t offset;

	int shift = 0, maxshift;

	int shift = 0, maxshift;

	unsigned int action;

	unsigned long flags;

	unsigned long flags;





	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	raw_spin_lock_irqsave(&timekeeper_lock, flags);
@@ -1406,7 +1411,7 @@ static void update_wall_time(void) 
	 * Finally, make sure that after the rounding

	 * Finally, make sure that after the rounding

	 * xtime_nsec isn't larger than NSEC_PER_SEC

	 * xtime_nsec isn't larger than NSEC_PER_SEC

	 */

	 */

	accumulate_nsecs_to_secs(tk);

	action = accumulate_nsecs_to_secs(tk);





	write_seqcount_begin(&timekeeper_seq);

	write_seqcount_begin(&timekeeper_seq);

	/* Update clock->cycle_last with the new value */

	/* Update clock->cycle_last with the new value */
@@ -1422,7 +1427,7 @@ static void update_wall_time(void) 
	 * updating.

	 * updating.

	 */

	 */

	memcpy(real_tk, tk, sizeof(*tk));

	memcpy(real_tk, tk, sizeof(*tk));

	timekeeping_update(real_tk, 0);

	timekeeping_update(real_tk, action);

	write_seqcount_end(&timekeeper_seq);

	write_seqcount_end(&timekeeper_seq);

out:

out:

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
@@ -1684,6 +1689,7 @@ int do_adjtimex(struct timex *txc) 




	if (tai != orig_tai) {

	if (tai != orig_tai) {

		__timekeeping_set_tai_offset(tk, tai);

		__timekeeping_set_tai_offset(tk, tai);

		update_pvclock_gtod(tk, true);

		clock_was_set_delayed();

		clock_was_set_delayed();

	}

	}

	write_seqcount_end(&timekeeper_seq);

	write_seqcount_end(&timekeeper_seq);

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