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Subject: [PATCH] clocksource: Fix thinko in watchdog selection
From: Thomas Gleixner <tglx@linutronix.de>
Reply-To: tglx@linutronix.de
To: LKML <linux-kernel@vger.kernel.org>
Cc: Adrian Bunk <bunk@stusta.de>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@elte.hu>,
       David L <idht4n@hotmail.com>, john stultz <johnstul@us.ibm.com>
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Date: Sun, 25 Mar 2007 14:42:51 +0200
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The watchdog implementation excludes low res / non continuous
clocksources from being selected as a watchdog reference
unintentionally.

Allow using jiffies/PIT as a watchdog reference as long as no better
clocksource is available. This is necessary to detect TSC breakage on
systems, which have no pmtimer/hpet.

The main goal of the initial patch (preventing to switch to highres/nohz
when no reliable fallback clocksource is available) is still guaranteed
by the checks in clocksource_watchdog().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 5b0e46b..fe5c7db 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -151,7 +151,8 @@ static void clocksource_check_watchdog(struct clocksource *cs)
 			watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
 			add_timer(&watchdog_timer);
 		}
-	} else if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) {
+	} else {
+		if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
 			cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
 
 		if (!watchdog || cs->rating > watchdog->rating) {