sched: x86, track TSC-unstable events

[deliverable/linux.git] / arch / i386 / kernel / tsc.c

diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index f64b81f3033bcba88ff47d268e8819b93d938e47..ea63a30ca3e88daa1bca2975f3c9f98812d7dffc 100644 (file)
--- a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -4,6 +4,7 @@
  * See comments there for proper credits.
  */
 
+#include <linux/sched.h>
 #include <linux/clocksource.h>
 #include <linux/workqueue.h>
 #include <linux/cpufreq.h>
@@ -106,8 +107,13 @@ unsigned long long sched_clock(void)
 
        /*
         * Fall back to jiffies if there's no TSC available:
+        * ( But note that we still use it if the TSC is marked
+        *   unstable. We do this because unlike Time Of Day,
+        *   the scheduler clock tolerates small errors and it's
+        *   very important for it to be as fast as the platform
+        *   can achive it. )
         */
-       if (unlikely(!tsc_enabled))
+       if (unlikely(!tsc_enabled && !tsc_unstable))
                /* No locking but a rare wrong value is not a big deal: */
                return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
 
@@ -277,6 +283,7 @@ static struct clocksource clocksource_tsc = {
 
 void mark_tsc_unstable(char *reason)
 {
+       sched_clock_unstable_event();
        if (!tsc_unstable) {
                tsc_unstable = 1;
                tsc_enabled = 0;