Attachment 603993 Details for Bug 840949 – RHEL PATCH 3/3

[patch] RHEL PATCH 3/3

0003-RHEL6.2.z-PATCH-BZ-847365-3-3-timekeeping-Fix-leapse.patch (text/plain), 2.65 KB, created by Prarit Bhargava on 2012-08-13 12:55:11 UTC

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Creator: Prarit Bhargava

Created: 2012-08-13 12:55:11 UTC

Size: 2.65 KB

patch

obsolete

>From cbd54c469ea158e2ebbf3793766ce946909a2501 Mon Sep 17 00:00:00 2001
>From: Prarit Bhargava <prarit@redhat.com>
>Date: Tue, 24 Jul 2012 10:23:22 -0400
>Subject: [PATCH 3/3] [RHEL6.2.z PATCH BZ 847365 3/3] timekeeping: Fix
> leapsecond triggered load spike issue
>
>Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=840949
>Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=847365
>
>commit 4873fa070ae84a4115f0b3c9dfabc224f1bc7c51
>Author: John Stultz <johnstul@us.ibm.com>
>Date:   Tue Jul 10 18:43:20 2012 -0400
>
>    timekeeping: Fix leapsecond triggered load spike issue
>
>    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>
>    Cc: stable@vger.kernel.org
>    Link: http://lkml.kernel.org/r/1341960205-56738-3-git-send-email-johnstul@us.ibm.com
>    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>
>In this minimal patchset I thought it was okay to call
>clock_was_set_delayed() whenever there was an overflow.  Of course, this
>is incorrect, and clock_was_set_delayed() should only be called when we're
>actually inserting a leap second.
>---
> kernel/time/timekeeping.c |    1 +
> 1 file changed, 1 insertion(+)
>
>diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
>index bae541b..ef67377 100644
>--- a/kernel/time/timekeeping.c
>+++ b/kernel/time/timekeeping.c
>@@ -180,6 +180,7 @@ void timekeeping_leap_insert(int leapsecond)
> 	wall_to_monotonic.tv_sec -= leapsecond;
> 	update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult);
> 	write_sequnlock(&xtime_lock);
>+	clock_was_set_delayed();
> }
> 
> #ifdef CONFIG_GENERIC_TIME
>-- 
>1.7.9.3
>

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