From 22f4bbcfb131e2392c78ad67af35fdd436d4dd54 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 17 Jul 2012 13:33:56 -0400 Subject: timekeeping: Provide hrtimer update function This is a backport of f6c06abfb3972ad4914cef57d8348fcb2932bc3b 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: Thomas Gleixner Reviewed-by: Ingo Molnar Acked-by: Peter Zijlstra Acked-by: Prarit Bhargava Signed-off-by: John Stultz Link: http://lkml.kernel.org/r/1341960205-56738-7-git-send-email-johnstul@us.ibm.com Signed-off-by: Thomas Gleixner Cc: Prarit Bhargava Cc: Thomas Gleixner Signed-off-by: John Stultz Signed-off-by: Greg Kroah-Hartman --- kernel/time/timekeeping.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) (limited to 'kernel/time') diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index d647773..f0c7565 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1126,6 +1126,40 @@ void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim, } while (read_seqretry(&xtime_lock, seq)); } +#ifdef CONFIG_HIGH_RES_TIMERS +/** + * ktime_get_update_offsets - hrtimer helper + * @real: pointer to storage for monotonic -> realtime offset + * @_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 *real, ktime_t *boot) +{ + ktime_t now; + unsigned int seq; + u64 secs, nsecs; + + do { + seq = read_seqbegin(&xtime_lock); + + secs = xtime.tv_sec; + nsecs = xtime.tv_nsec; + nsecs += timekeeping_get_ns(); + /* If arch requires, add in gettimeoffset() */ + nsecs += arch_gettimeoffset(); + + *real = offs_real; + *boot = offs_boot; + } while (read_seqretry(&xtime_lock, seq)); + + now = ktime_add_ns(ktime_set(secs, 0), nsecs); + now = ktime_sub(now, *real); + return now; +} +#endif + /** * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format */ -- cgit v1.1