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    Subject[PATCH 0/3] Fix for leapsecond caused hrtimer/futex issue
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    Thomas:
    So Prarit and my testing over the last few days have gone fine,
    and its been quiet otherwise, so I wanted to go ahead and submit this
    for inclusion.

    As widely reported on the internet, many Linux systems after
    the leapsecond was inserted experienced futex related load
    spikes (usually connected to MySQL, Firefox, Thunderbird, Java, etc).

    An apparent workaround for this issue is running:
    $ date -s "`date`"

    Credit: http://www.sheeri.com/content/mysql-and-leap-second-high-cpu-and-fix


    This issue stemmed from the timekeeping subsystem not notifying
    the hrtimer subsystem that the leapsecond occurred, causing
    CLOCK_REALTIME hritmers to be fired one second early, and
    sub-second CLOCK_REALTIME hrtimer timeouts to fire immediately
    (causing the load spikes).


    To address this issue I'm proposing we do three things:
    1) Fix the clock_was_set() call to remove the limitation that kept
    us from calling it from update_wall_time().

    2) Call clock_was_set() when we add/remove a leapsecond.

    3) Change hrtimer_interrupt to update the hrtimer base offset values.
    This third item provides additional robustness should the
    clock_was_set() notification (done via a timer if we're in_atomic)
    be delayed significantly.


    NOTE: Some reports have been of a hard hang right at or before
    the leapsecond. I've not been able to reproduce or diagnose
    this, so this fix does not likely address the reported hard
    hangs (unless they end up being connected to the futex/hrtimer
    issue). Please email lkml and me if you experienced this.

    Big thanks to Prarit for shaking out a few issues in the earlier
    version of this patch set, as well as the extra effort testing over
    the Holiday!

    Also, I've already got backports generated for -stable, that I'm
    testing and I'll submitting them once I have upstream commit ids for
    these patches.

    thanks
    -john

    CC: Prarit Bhargava <prarit@redhat.com>
    CC: stable@vger.kernel.org
    CC: Thomas Gleixner <tglx@linutronix.de>


    John Stultz (3):
    hrtimer: Fix clock_was_set so it is safe to call from irq context
    time: Fix leapsecond triggered hrtimer/futex load spike issue
    hrtimer: Update hrtimer base offsets each hrtimer_interrupt

    include/linux/hrtimer.h | 3 +++
    kernel/hrtimer.c | 31 +++++++++++++++++++++++++++----
    kernel/time/timekeeping.c | 38 ++++++++++++++++++++++++++++++++++++++
    3 files changed, 68 insertions(+), 4 deletions(-)

    --
    1.7.9.5



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