linux-kernel - [PATCH 1/8] ntp: Fix STA

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Date:	Fri, 13 Jul 2012 01:21:50 -0400
From:	John Stultz <john.stultz@...aro.org>
To:	Linux Kernel <linux-kernel@...r.kernel.org>
Cc:	John Stultz <johnstul@...ibm.com>, Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Richard Cochran <richardcochran@...il.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>, stable@...r.kernel.org
Subject: [PATCH 1/8] ntp: Fix STA_INS/DEL clearing bug

From: John Stultz <johnstul@...ibm.com>

In commit 6b43ae8a619d17c4935c3320d2ef9e92bdeed05d, I
introduced a bug that kept the STA_INS or STA_DEL bit
from being cleared from time_status via adjtimex()
without forcing STA_PLL first.

Usually once the STA_INS is set, it isn't cleared
until the leap second is applied, so its unlikely this
affected anyone. However during testing I noticed it
took some effort to cancel a leap second once STA_INS
was set.

This issue affects 3.4 and up.

Since this isn't urgent (issue is only observed in testing,
the behavior doesn't affect ntpd, nor is a leapsecond due
for at least ~6 months), and we're late in the 3.5-rc
cycle, I'm holding this off for 3.6 merge window,
where I'll then backport to 3.5-stable and 3.4-stable.

CC: Ingo Molnar <mingo@...nel.org>
CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC: Richard Cochran <richardcochran@...il.com>
CC: Prarit Bhargava <prarit@...hat.com>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: stable@...r.kernel.org
Signed-off-by: John Stultz <johnstul@...ibm.com>
---
 kernel/time/ntp.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 70b33ab..b7fbadc 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -409,7 +409,9 @@ int second_overflow(unsigned long secs)
 			time_state = TIME_DEL;
 		break;
 	case TIME_INS:
-		if (secs % 86400 == 0) {
+		if (!(time_status & STA_INS))
+			time_state = TIME_OK;
+		else if (secs % 86400 == 0) {
 			leap = -1;
 			time_state = TIME_OOP;
 			time_tai++;
@@ -418,7 +420,9 @@ int second_overflow(unsigned long secs)
 		}
 		break;
 	case TIME_DEL:
-		if ((secs + 1) % 86400 == 0) {
+		if (!(time_status & STA_DEL))
+			time_state = TIME_OK;
+		else if ((secs + 1) % 86400 == 0) {
 			leap = 1;
 			time_tai--;
 			time_state = TIME_WAIT;
-- 
1.7.9.5

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