linux-kernel - [PATCH 9/9] clocksource: Sanity check watchdog clocksource

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Message-Id: <1439844063-7957-10-git-send-email-john.stultz@linaro.org>
Date:	Mon, 17 Aug 2015 13:41:03 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Shaohua Li <shli@...com>, Prarit Bhargava <prarit@...hat.com>,
	Richard Cochran <richardcochran@...il.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	John Stultz <john.stultz@...aro.org>
Subject: [PATCH 9/9] clocksource: Sanity check watchdog clocksource

From: Shaohua Li <shli@...com>

Add a sanity check to make sure watchdog clocksource doesn't wrap too
quickly.

Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Richard Cochran <richardcochran@...il.com>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Shaohua Li <shli@...com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 kernel/time/clocksource.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 8417c83..64e4629 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -327,7 +327,8 @@ static void clocksource_enqueue_watchdog(struct clocksource *cs)
 		if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
 			cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
 		/* Pick the best watchdog. */
-		if (!watchdog || cs->rating > watchdog->rating) {
+		if (cs->max_idle_ns > WATCHDOG_MAX_INTERVAL_NS &&
+		    (!watchdog || cs->rating > watchdog->rating)) {
 			watchdog = cs;
 			/* Reset watchdog cycles */
 			clocksource_reset_watchdog();
-- 
1.9.1

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