[PATCH] clocksource: Add verification (watchdog) helper
The TSC needs to be verified against another clocksource. Instead of using
hardwired assumptions of available hardware, provide a generic verification
mechanism. The verification uses the best available clocksource and handles
the usability for high resolution timers / dynticks of the clocksource which
needs to be verified.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 2f6a3d6..3cb8ac9 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -63,9 +63,116 @@
finished_booting = 1;
return 0;
}
-
late_initcall(clocksource_done_booting);
+#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
+static LIST_HEAD(watchdog_list);
+static struct clocksource *watchdog;
+static struct timer_list watchdog_timer;
+static DEFINE_SPINLOCK(watchdog_lock);
+static cycle_t watchdog_last;
+/*
+ * Interval: 0.5sec Treshold: 0.0625s
+ */
+#define WATCHDOG_INTERVAL (HZ >> 1)
+#define WATCHDOG_TRESHOLD (NSEC_PER_SEC >> 4)
+
+static void clocksource_ratewd(struct clocksource *cs, int64_t delta)
+{
+ if (delta > -WATCHDOG_TRESHOLD && delta < WATCHDOG_TRESHOLD)
+ return;
+
+ printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
+ cs->name, delta);
+ cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
+ clocksource_change_rating(cs, 0);
+ cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
+ list_del(&cs->wd_list);
+}
+
+static void clocksource_watchdog(unsigned long data)
+{
+ struct clocksource *cs, *tmp;
+ cycle_t csnow, wdnow;
+ int64_t wd_nsec, cs_nsec;
+
+ spin_lock(&watchdog_lock);
+
+ wdnow = watchdog->read();
+ wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask);
+ watchdog_last = wdnow;
+
+ list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
+ csnow = cs->read();
+ /* 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;
+ }
+ 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);
+ }
+ }
+
+ if (!list_empty(&watchdog_list)) {
+ __mod_timer(&watchdog_timer,
+ watchdog_timer.expires + WATCHDOG_INTERVAL);
+ }
+ spin_unlock(&watchdog_lock);
+}
+static void clocksource_check_watchdog(struct clocksource *cs)
+{
+ struct clocksource *cse;
+ unsigned long flags;
+
+ spin_lock_irqsave(&watchdog_lock, flags);
+ if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
+ int started = !list_empty(&watchdog_list);
+
+ list_add(&cs->wd_list, &watchdog_list);
+ if (!started && watchdog) {
+ watchdog_last = watchdog->read();
+ watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
+ add_timer(&watchdog_timer);
+ }
+ } else if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) {
+ cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
+
+ if (!watchdog || cs->rating > watchdog->rating) {
+ if (watchdog)
+ del_timer(&watchdog_timer);
+ watchdog = cs;
+ init_timer(&watchdog_timer);
+ watchdog_timer.function = clocksource_watchdog;
+
+ /* Reset watchdog cycles */
+ list_for_each_entry(cse, &watchdog_list, wd_list)
+ cse->flags &= ~CLOCK_SOURCE_WATCHDOG;
+ /* Start if list is not empty */
+ if (!list_empty(&watchdog_list)) {
+ watchdog_last = watchdog->read();
+ watchdog_timer.expires =
+ jiffies + WATCHDOG_INTERVAL;
+ add_timer(&watchdog_timer);
+ }
+ }
+ }
+ spin_unlock_irqrestore(&watchdog_lock, flags);
+}
+#else
+static void clocksource_check_watchdog(struct clocksource *cs)
+{
+ if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
+ cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
+}
+#endif
+
/**
* clocksource_get_next - Returns the selected clocksource
*
@@ -94,13 +201,21 @@
*/
static struct clocksource *select_clocksource(void)
{
+ struct clocksource *next;
+
if (list_empty(&clocksource_list))
return NULL;
if (clocksource_override)
- return clocksource_override;
+ next = clocksource_override;
+ else
+ next = list_entry(clocksource_list.next, struct clocksource,
+ list);
- return list_entry(clocksource_list.next, struct clocksource, list);
+ if (next == curr_clocksource)
+ return NULL;
+
+ return next;
}
/*
@@ -138,13 +253,15 @@
int clocksource_register(struct clocksource *c)
{
unsigned long flags;
- int ret = 0;
+ int ret;
spin_lock_irqsave(&clocksource_lock, flags);
ret = clocksource_enqueue(c);
if (!ret)
next_clocksource = select_clocksource();
spin_unlock_irqrestore(&clocksource_lock, flags);
+ if (!ret)
+ clocksource_check_watchdog(c);
return ret;
}
EXPORT_SYMBOL(clocksource_register);
@@ -159,6 +276,7 @@
spin_lock_irqsave(&clocksource_lock, flags);
list_del(&cs->list);
+ cs->rating = rating;
clocksource_enqueue(cs);
next_clocksource = select_clocksource();
spin_unlock_irqrestore(&clocksource_lock, flags);