From patchwork Mon Jul 23 17:24:37 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [09/11] 2.6.32.x: timekeeping: Provide hrtimer update function Date: Mon, 23 Jul 2012 07:24:37 -0000 From: Luis Henriques X-Patchwork-Id: 172724 Message-Id: <1343064279-28091-10-git-send-email-luis.henriques@canonical.com> To: kernel-team@lists.ubuntu.com From: Thomas Gleixner BugLink: http://bugs.launchpad.net/bugs/1020285 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 Cc: stable@vger.kernel.org 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 Cc: Linux Kernel Signed-off-by: John Stultz Signed-off-by: Luis Henriques --- include/linux/hrtimer.h | 2 +- kernel/time/timekeeping.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 33 insertions(+), 1 deletion(-) diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index a7f48af..b4f0b3f 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -319,7 +319,7 @@ static inline void clock_was_set_delayed(void) { } extern ktime_t ktime_get(void); extern ktime_t ktime_get_real(void); - +extern ktime_t ktime_get_update_offsets(ktime_t *offs_real); DECLARE_PER_CPU(struct tick_device, tick_cpu_device); diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index c7fbc9f..6054b94 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -943,3 +943,35 @@ struct timespec get_monotonic_coarse(void) now.tv_nsec + mono.tv_nsec); return now; } + +#ifdef CONFIG_HIGH_RES_TIMERS +/** + * ktime_get_update_offsets - hrtimer helper + * @real: pointer to storage for monotonic -> realtime 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 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; + } while (read_seqretry(&xtime_lock, seq)); + + now = ktime_add_ns(ktime_set(secs, 0), nsecs); + now = ktime_sub(now, *real); + return now; +} +#endif