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Commit c528f7c6 authored by John Stultz's avatar John Stultz Committed by Thomas Gleixner
Browse files

time: Introduce timekeeping_inject_offset 



This adds a kernel-internal timekeeping interface to add or subtract
a fixed amount from CLOCK_REALTIME. This makes it so kernel users or
interfaces trying to do so do not have to read the time, then add an
offset and then call settimeofday(), which adds some extra error in
comparision to just simply adding the offset in the kernel timekeeping
core.

Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Signed-off-by: default avatarRichard Cochran <richard.cochran@omicron.at>
LKML-Reference: <20110201134419.584311693@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 0061748d

include/linux/time.h

+1 −0
Original line number Diff line number Diff line
@@ -166,6 +166,7 @@ extern struct timespec timespec_trunc(struct timespec t, unsigned gran); 
extern int timekeeping_valid_for_hres(void);

extern u64 timekeeping_max_deferment(void);

extern void timekeeping_leap_insert(int leapsecond);

extern int timekeeping_inject_offset(struct timespec *ts);



struct tms;

extern void do_sys_times(struct tms *);

kernel/time/timekeeping.c

+36 −0
Original line number Diff line number Diff line
@@ -387,6 +387,42 @@ int do_settimeofday(const struct timespec *tv) 


EXPORT_SYMBOL(do_settimeofday);





/**

 * timekeeping_inject_offset - Adds or subtracts from the current time.

 * @tv:		pointer to the timespec variable containing the offset

 *

 * Adds or subtracts an offset value from the current time.

 */

int timekeeping_inject_offset(struct timespec *ts)

{

	unsigned long flags;



	if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)

		return -EINVAL;



	write_seqlock_irqsave(&xtime_lock, flags);



	timekeeping_forward_now();



	xtime = timespec_add(xtime, *ts);

	wall_to_monotonic = timespec_sub(wall_to_monotonic, *ts);



	timekeeper.ntp_error = 0;

	ntp_clear();



	update_vsyscall(&xtime, &wall_to_monotonic, timekeeper.clock,

				timekeeper.mult);



	write_sequnlock_irqrestore(&xtime_lock, flags);



	/* signal hrtimers about time change */

	clock_was_set();



	return 0;

}

EXPORT_SYMBOL(timekeeping_inject_offset);



/**

 * change_clocksource - Swaps clocksources if a new one is available

 *