From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757707Ab2GRAHB (ORCPT ); Tue, 17 Jul 2012 20:07:01 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:48276 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757534Ab2GRAFA (ORCPT ); Tue, 17 Jul 2012 20:05:00 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg KH , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, John Stultz , Jan Engelhardt , Ingo Molnar , Peter Zijlstra , Prarit Bhargava , Thomas Gleixner Subject: [ 31/37] timekeeping: Fix leapsecond triggered load spike issue Date: Tue, 17 Jul 2012 17:03:08 -0700 Message-Id: <20120717232433.995025566@linuxfoundation.org> X-Mailer: git-send-email 1.7.10.1.362.g242cab3 In-Reply-To: <20120717232431.399005532@linuxfoundation.org> References: <20120717232455.GA5994@kroah.com> <20120717232431.399005532@linuxfoundation.org> User-Agent: quilt/0.60-20.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Greg KH 3.4-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-johnstul@us.ibm.com Signed-off-by: Thomas Gleixner Cc: Prarit Bhargava Cc: Thomas Gleixner Signed-off-by: John Stultz Signed-off-by: Greg Kroah-Hartman --- kernel/time/timekeeping.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -965,6 +965,8 @@ static cycle_t logarithmic_accumulation( leap = second_overflow(timekeeper.xtime.tv_sec); timekeeper.xtime.tv_sec += leap; timekeeper.wall_to_monotonic.tv_sec -= leap; + if (leap) + clock_was_set_delayed(); } /* Accumulate raw time */ @@ -1081,6 +1083,8 @@ static void update_wall_time(void) leap = second_overflow(timekeeper.xtime.tv_sec); timekeeper.xtime.tv_sec += leap; timekeeper.wall_to_monotonic.tv_sec -= leap; + if (leap) + clock_was_set_delayed(); } timekeeping_update(false);