linux-kernel - Patch "timekeeping: Fix leapsecond triggered load spike issue" has been added to the 3.0-stable tree

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Date:	Tue, 17 Jul 2012 15:49:58 -0700
From:	<gregkh@...uxfoundation.org>
To:	johnstul@...ibm.com, a.p.zijlstra@...llo.nl,
	gregkh@...uxfoundation.org, jengelh@...i.de,
	linux-kernel@...r.kernel.org, mingo@...nel.org, prarit@...hat.com,
	tglx@...utronix.de
Cc:	<stable@...r.kernel.org>, <stable-commits@...r.kernel.org>
Subject: Patch "timekeeping: Fix leapsecond triggered load spike issue" has been added to the 3.0-stable tree


This is a note to let you know that I've just added the patch titled

    timekeeping: Fix leapsecond triggered load spike issue

to the 3.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     timekeeping-fix-leapsecond-triggered-load-spike-issue.patch
and it can be found in the queue-3.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@...r.kernel.org> know about it.


>From johnstul@...ibm.com  Tue Jul 17 15:25:50 2012
From: John Stultz <johnstul@...ibm.com>
Date: Tue, 17 Jul 2012 13:33:53 -0400
Subject: timekeeping: Fix leapsecond triggered load spike issue
To: stable@...r.kernel.org
Cc: John Stultz <johnstul@...ibm.com>, Thomas Gleixner <tglx@...utronix.de>, Prarit Bhargava <prarit@...hat.com>, Linux Kernel <linux-kernel@...r.kernel.org>
Message-ID: <1342546438-17534-7-git-send-email-johnstul@...ibm.com>

From: John Stultz <johnstul@...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 <johnstul@...ibm.com>
Reported-by: Jan Engelhardt <jengelh@...i.de>
Reviewed-by: Ingo Molnar <mingo@...nel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Acked-by: Prarit Bhargava <prarit@...hat.com>
Link: http://lkml.kernel.org/r/1341960205-56738-3-git-send-email-johnstul@us.ibm.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: John Stultz <johnstul@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/time/timekeeping.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -827,6 +827,8 @@ static cycle_t logarithmic_accumulation(
 		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);


Patches currently in stable-queue which might be from johnstul@...ibm.com are

queue-3.0/timekeeping-fix-leapsecond-triggered-load-spike-issue.patch
queue-3.0/time-move-common-updates-to-a-function.patch
queue-3.0/timekeeping-fix-clock_monotonic-inconsistency-during-leapsecond.patch
queue-3.0/hrtimer-update-hrtimer-base-offsets-each-hrtimer_interrupt.patch
queue-3.0/timekeeping-add-missing-update-call-in-timekeeping_resume.patch
queue-3.0/hrtimers-move-lock-held-region-in-hrtimer_interrupt.patch
queue-3.0/hrtimer-provide-clock_was_set_delayed.patch
queue-3.0/ntp-fix-leap-second-hrtimer-livelock.patch
queue-3.0/timekeeping-provide-hrtimer-update-function.patch
queue-3.0/timekeeping-maintain-ktime_t-based-offsets-for-hrtimers.patch
queue-3.0/ntp-correct-tai-offset-during-leap-second.patch
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