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authorJohn Stultz <johnstul@us.ibm.com>2012-07-17 13:33:53 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-07-19 08:58:43 -0700
commitd21e4baf4523fec26e3c70cb78b013ad3b245c83 (patch)
treef8d352b8409ca5db185e02db346f165ffff1d29e /kernel
parent62b787f886e2d96cc7c5428aeee05dbe32a9531b (diff)
timekeeping: Fix leapsecond triggered load spike issue
This is a backport of 4873fa070ae84a4115f0b3c9dfabc224f1bc7c51 The timekeeping code misses an update of the hrtimer subsystem after a leap second happened. Due to that timers based on CLOCK_REALTIME are either expiring a second early or late depending on whether a leap second has been inserted or deleted until an operation is initiated which causes that update. Unless the update happens by some other means this discrepancy between the timekeeping and the hrtimer data stays forever and timers are expired either early or late. The reported immediate workaround - $ data -s "`date`" - is causing a call to clock_was_set() which updates the hrtimer data structures. See: http://www.sheeri.com/content/mysql-and-leap-second-high-cpu-and-fix Add the missing clock_was_set() call to update_wall_time() in case of a leap second event. The actual update is deferred to softirq context as the necessary smp function call cannot be invoked from hard interrupt context. Signed-off-by: John Stultz <johnstul@us.ibm.com> Reported-by: Jan Engelhardt <jengelh@inai.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Prarit Bhargava <prarit@redhat.com> Link: http://lkml.kernel.org/r/1341960205-56738-3-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> Signed-off-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/timekeeping.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 0b582ebeb7cc..92014744e524 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -827,6 +827,8 @@ static cycle_t logarithmic_accumulation(cycle_t offset, int shift)
leap = second_overflow(xtime.tv_sec);
xtime.tv_sec += leap;
wall_to_monotonic.tv_sec -= leap;
+ if (leap)
+ clock_was_set_delayed();
}
/* Accumulate raw time */
@@ -938,6 +940,8 @@ static void update_wall_time(void)
leap = second_overflow(xtime.tv_sec);
xtime.tv_sec += leap;
wall_to_monotonic.tv_sec -= leap;
+ if (leap)
+ clock_was_set_delayed();
}
timekeeping_update(false);