[PATCH 3.2 17/60] clocksource: Fix abs() usage w/ 64bit values

From: Ben Hutchings
Date: Sat Nov 14 2015 - 21:21:14 EST

3.2.73-rc1 review patch. If anyone has any objections, please let me know.


From: John Stultz <john.stultz@xxxxxxxxxx>

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@xxxxxxxxxx>
Cc: Prarit Bhargava <prarit@xxxxxxxxxx>
Cc: Richard Cochran <richardcochran@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1442279124-7309-2-git-send-email-john.stultz@xxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
kernel/time/clocksource.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -291,7 +291,7 @@ static void clocksource_watchdog(unsigne

/* Check the deviation from the watchdog clocksource. */
- if ((abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD)) {
+ if (abs64(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) {
clocksource_unstable(cs, cs_nsec - wd_nsec);

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/