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authorIngo Molnar <mingo@elte.hu>2007-07-09 18:51:59 +0200
committerIngo Molnar <mingo@elte.hu>2007-07-09 18:51:59 +0200
commitbb29ab26863c022743143f27956cc0ca362f258c (patch)
treef8106b8a82d4abe9c3b217c7ca96307539a945ad /arch/i386
parentdd41f596cda0d7d6e4a8b139ffdfabcefdd46528 (diff)
sched: x86, track TSC-unstable events
track TSC-unstable events and propagate it to the scheduler code. Also allow sched_clock() to be used when the TSC is unstable, the rq_clock() wrapper creates a reliable clock out of it. Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/i386')
-rw-r--r--arch/i386/kernel/tsc.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index f64b81f3033..ea63a30ca3e 100644
--- 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;