lkml.org 
[lkml]   [2012]   [Oct]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[ 016/180] 2.6.32.x: timekeeping: Provide hrtimer update function
    2.6.32-longterm review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Thomas Gleixner <tglx@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 <tglx@linutronix.de>
    Reviewed-by: Ingo Molnar <mingo@kernel.org>
    Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Acked-by: Prarit Bhargava <prarit@redhat.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: John Stultz <johnstul@us.ibm.com>
    Link: http://lkml.kernel.org/r/1341960205-56738-7-git-send-email-johnstul@us.ibm.com
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Prarit Bhargava <prarit@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Linux Kernel <linux-kernel@vger.kernel.org>
    Signed-off-by: John Stultz <johnstul@us.ibm.com>
    Signed-off-by: Willy Tarreau <w@1wt.eu>
    ---
    include/linux/hrtimer.h | 2 +-
    kernel/time/timekeeping.c | 32 ++++++++++++++++++++++++++++++++
    2 files changed, 33 insertions(+), 1 deletions(-)

    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
    --
    1.7.2.1.45.g54fbc




    \
     
     \ /
      Last update: 2012-10-02 08:41    [W:4.292 / U:0.064 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site