From: Thomas Gleixner <t...@linutronix.de> 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 <t...@linutronix.de> Reviewed-by: Ingo Molnar <mi...@kernel.org> Acked-by: Peter Zijlstra <a.p.zijls...@chello.nl> Acked-by: Prarit Bhargava <pra...@redhat.com> Cc: sta...@vger.kernel.org Signed-off-by: John Stultz <johns...@us.ibm.com> Link: http://lkml.kernel.org/r/1341960205-56738-7-git-send-email-johns...@us.ibm.com Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: Prarit Bhargava <pra...@redhat.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Linux Kernel <linux-kernel@vger.kernel.org> Signed-off-by: John Stultz <johns...@us.ibm.com> --- include/linux/hrtimer.h | 1 + kernel/time/timekeeping.c | 34 ++++++++++++++++++++++++++++++++++ 2 files changed, 35 insertions(+) diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index c9ec940..cc07d27 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -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); diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index d5d0e5d..4938c5e 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1240,6 +1240,40 @@ 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 */ -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
