linux-kernel - [PATCH 4.2 236/258] clocksource: Fix abs() usage w/ 64bit values

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Message-Id: <20151018014741.139385937@linuxfoundation.org>
Date:	Sat, 17 Oct 2015 18:59:09 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, John Stultz <john.stultz@...aro.org>,
	Prarit Bhargava <prarit@...hat.com>,
	Richard Cochran <richardcochran@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 4.2 236/258] clocksource: Fix abs() usage w/ 64bit values

4.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: John Stultz <john.stultz@...aro.org>

commit 67dfae0cd72fec5cd158b6e5fb1647b7dbe0834c upstream.

This patch fixes one cases where abs() was being used with 64-bit
nanosecond values, where the result may be capped at 32-bits.

This potentially could cause watchdog false negatives on 32-bit
systems, so this patch addresses the issue by using abs64().

Signed-off-by: John Stultz <john.stultz@...aro.org>
Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Richard Cochran <richardcochran@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>
Link: http://lkml.kernel.org/r/1442279124-7309-2-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/time/clocksource.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -217,7 +217,7 @@ static void clocksource_watchdog(unsigne
 			continue;
 
 		/* Check the deviation from the watchdog clocksource. */
-		if ((abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD)) {
+		if (abs64(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) {
 			pr_warn("timekeeping watchdog: Marking clocksource '%s' as unstable because the skew is too large:\n",
 				cs->name);
 			pr_warn("                      '%s' wd_now: %llx wd_last: %llx mask: %llx\n",


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