clocksource: Delay clocksource watchdog highres enablement

The clocksource watchdog marks a clock as highres capable before it
checked the deviation from the watchdog clocksource even for a single
time. Make sure that the deviation is at least checked once before
doing the switch to highres mode.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134808.627795883@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 22 insertions, 25 deletions

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index e91662e87cde..76256c5aecb8 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -153,11 +153,8 @@ static unsigned long watchdog_resumed;
 #define WATCHDOG_INTERVAL (HZ >> 1)
 #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
 
-static void clocksource_ratewd(struct clocksource *cs, int64_t delta)
+static void clocksource_unstable(struct clocksource *cs, int64_t delta)
 {
-        if (delta > -WATCHDOG_THRESHOLD && delta < WATCHDOG_THRESHOLD)
-                return;
-
         printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
                cs->name, delta);
         cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
@@ -183,31 +180,31 @@ static void clocksource_watchdog(unsigned long data)
         list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
                 csnow = cs->read(cs);
 
-                if (unlikely(resumed)) {
+                /* Clocksource initialized ? */
+                if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
+                        cs->flags |= CLOCK_SOURCE_WATCHDOG;
                         cs->wd_last = csnow;
                         continue;
                 }
 
-                /* Initialized ? */
-                if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
-                        if ((cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
-                            (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
-                                cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
-                                /*
-                                 * We just marked the clocksource as
-                                 * highres-capable, notify the rest of the
-                                 * system as well so that we transition
-                                 * into high-res mode:
-                                 */
-                                tick_clock_notify();
-                        }
-                        cs->flags |= CLOCK_SOURCE_WATCHDOG;
-                        cs->wd_last = csnow;
-                } else {
-                        cs_nsec = cyc2ns(cs, (csnow - cs->wd_last) & cs->mask);
-                        cs->wd_last = csnow;
-                        /* Check the delta. Might remove from the list ! */
-                        clocksource_ratewd(cs, cs_nsec - wd_nsec);
+                /* Check the deviation from the watchdog clocksource. */
+                cs_nsec = cyc2ns(cs, (csnow - cs->wd_last) & cs->mask);
+                cs->wd_last = csnow;
+                if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) {
+                        clocksource_unstable(cs, cs_nsec - wd_nsec);
+                        continue;
+                }
+
+                if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
+                    (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
+                    (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
+                        cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
+                        /*
+                         * We just marked the clocksource as highres-capable,
+                         * notify the rest of the system as well so that we
+                         * transition into high-res mode:
+                         */
+                        tick_clock_notify();
                 }
         }