Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit f6c06abf authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

timekeeping: Provide hrtimer update function 



To finally fix the infamous leap second issue and other race windows
caused by functions which change the offsets between the various time
bases (CLOCK_MONOTONIC, CLOCK_REALTIME and CLOCK_BOOTTIME) we need a
function which atomically gets the current monotonic time and updates
the offsets of CLOCK_REALTIME and CLOCK_BOOTTIME with minimalistic
overhead. The previous patch which provides ktime_t offsets allows us
to make this function almost as cheap as ktime_get() which is going to
be replaced in hrtimer_interrupt().

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: default avatarPrarit Bhargava <prarit@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarJohn Stultz <johnstul@us.ibm.com>
Link: http://lkml.kernel.org/r/1341960205-56738-7-git-send-email-johnstul@us.ibm.com


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 196951e9

include/linux/hrtimer.h

+1 −0
Original line number Diff line number Diff line
@@ -327,6 +327,7 @@ extern ktime_t ktime_get(void); 
extern ktime_t ktime_get_real(void);

extern ktime_t ktime_get_boottime(void);

extern ktime_t ktime_get_monotonic_offset(void);

extern ktime_t ktime_get_update_offsets(ktime_t *offs_real, ktime_t *offs_boot);



DECLARE_PER_CPU(struct tick_device, tick_cpu_device);

kernel/time/timekeeping.c

+34 −0
Original line number Diff line number Diff line
@@ -1271,6 +1271,40 @@ void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim, 
	} while (read_seqretry(&timekeeper.lock, seq));

}



#ifdef CONFIG_HIGH_RES_TIMERS

/**

 * ktime_get_update_offsets - hrtimer helper

 * @offs_real:	pointer to storage for monotonic -> realtime offset

 * @offs_boot:	pointer to storage for monotonic -> boottime offset

 *

 * Returns current monotonic time and updates the offsets

 * Called from hrtimer_interupt() or retrigger_next_event()

 */

ktime_t ktime_get_update_offsets(ktime_t *offs_real, ktime_t *offs_boot)

{

	ktime_t now;

	unsigned int seq;

	u64 secs, nsecs;



	do {

		seq = read_seqbegin(&timekeeper.lock);



		secs = timekeeper.xtime.tv_sec;

		nsecs = timekeeper.xtime.tv_nsec;

		nsecs += timekeeping_get_ns();

		/* If arch requires, add in gettimeoffset() */

		nsecs += arch_gettimeoffset();



		*offs_real = timekeeper.offs_real;

		*offs_boot = timekeeper.offs_boot;

	} while (read_seqretry(&timekeeper.lock, seq));



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

	now = ktime_sub(now, *offs_real);

	return now;

}

#endif



/**

 * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format

 */