[ 079/108] timekeeping: Fix leapsecond triggered load spike issue
3.2-stable review patch. If anyone has any objections, please let me know. -- From: John Stultz 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 Reported-by: Jan Engelhardt Reviewed-by: Ingo Molnar Acked-by: Peter Zijlstra Acked-by: Prarit Bhargava Link: http://lkml.kernel.org/r/1341960205-56738-3-git-send-email-johns...@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: Ben Hutchings --- kernel/time/timekeeping.c |4 1 file changed, 4 insertions(+) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 5d55185..8958ad7 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -941,6 +941,8 @@ 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 */ @@ -1052,6 +1054,8 @@ 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[ 079/108] timekeeping: Fix leapsecond triggered load spike issue
3.2-stable review patch. If anyone has any objections, please let me know. -- From: John Stultz johns...@us.ibm.com 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 johns...@us.ibm.com Reported-by: Jan Engelhardt jeng...@inai.de Reviewed-by: Ingo Molnar mi...@kernel.org Acked-by: Peter Zijlstra a.p.zijls...@chello.nl Acked-by: Prarit Bhargava pra...@redhat.com Link: http://lkml.kernel.org/r/1341960205-56738-3-git-send-email-johns...@us.ibm.com Signed-off-by: Thomas Gleixner t...@linutronix.de Cc: Prarit Bhargava pra...@redhat.com Cc: Thomas Gleixner t...@linutronix.de Cc: Linux Kernel linux-kernel@vger.kernel.org Signed-off-by: John Stultz johns...@us.ibm.com Signed-off-by: Ben Hutchings b...@decadent.org.uk --- kernel/time/timekeeping.c |4 1 file changed, 4 insertions(+) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 5d55185..8958ad7 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -941,6 +941,8 @@ 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 */ @@ -1052,6 +1054,8 @@ 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); -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
