revert "x86: tsc prevent time going backwards"
revert:
| commit 47001d603375f857a7fab0e9c095d964a1ea0039
| Author: Thomas Gleixner <tglx@linutronix.de>
| Date: Tue Apr 1 19:45:18 2008 +0200
|
| x86: tsc prevent time going backwards
it has been identified to cause suspend regression - and the
commit fixes a longstanding bug that existed before 2.6.25 was
opened - so it can wait some more until the effects are better
understood.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index d7498b3..f14cfd9 100644
--- a/arch/x86/kernel/tsc_32.c
+++ b/arch/x86/kernel/tsc_32.c
@@ -287,27 +287,14 @@
/* clock source code */
static unsigned long current_tsc_khz = 0;
-static struct clocksource clocksource_tsc;
-/*
- * We compare the TSC to the cycle_last value in the clocksource
- * structure to avoid a nasty time-warp issue. This can be observed in
- * a very small window right after one CPU updated cycle_last under
- * xtime lock and the other CPU reads a TSC value which is smaller
- * than the cycle_last reference value due to a TSC which is slighty
- * behind. This delta is nowhere else observable, but in that case it
- * results in a forward time jump in the range of hours due to the
- * unsigned delta calculation of the time keeping core code, which is
- * necessary to support wrapping clocksources like pm timer.
- */
static cycle_t read_tsc(void)
{
cycle_t ret;
rdtscll(ret);
- return ret >= clocksource_tsc.cycle_last ?
- ret : clocksource_tsc.cycle_last;
+ return ret;
}
static struct clocksource clocksource_tsc = {