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    Subject[PATCH 0/2][RFC] Potential fix for leapsecond caused futex issue (v2)
    From: John Stultz <>

    Here's round two on this one.

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

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


    To address this issue we do two 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.

    I've been able to reproduce the load spike using Thunderbird
    when triggering a leap second and with this patch the issue
    did not crop up.

    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

    * Chase down the futex/hrtimer interaction to see if this could
    be triggered in any other way.
    * Get Tglx's input/ack
    * Generate a backport for pre-v3.4 kernels

    * Address the issue w/ calling clock_was_set from atomic context, pointed
    out by Prarit and Ben.
    * Rework fix so its simpler.

    CC: Prarit Bhargava <>
    CC: Thomas Gleixner <>
    Reported-by: Jan Engelhardt <>
    Signed-off-by: John Stultz <>

    John Stultz (2):
    [RFC] Fix clock_was_set so it is safe to call from atomic
    [RFC] Fix leapsecond triggered hrtimer/futex load spike issue

    kernel/hrtimer.c | 16 +++++++++++++++-
    kernel/time/timekeeping.c | 4 ++++
    2 files changed, 19 insertions(+), 1 deletion(-)


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