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authorIngo Molnar <mingo@elte.hu>2008-04-07 20:58:08 +0200
committerIngo Molnar <mingo@elte.hu>2008-04-07 21:09:14 +0200
commit5b13d863573e746739ccfc24ac1a9473cfee8df1 (patch)
treeaa7f3536bf6f1c491a6051cf55b4ed71cd2a421c
parent4cac04dd63fa3b202ee313ed1afbbd135ab887ee (diff)
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>
-rw-r--r--arch/x86/kernel/tsc_32.c15
-rw-r--r--arch/x86/kernel/tsc_64.c23
2 files changed, 4 insertions, 34 deletions
diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index d7498b34c8e..f14cfd9d1f9 100644
--- a/arch/x86/kernel/tsc_32.c
+++ b/arch/x86/kernel/tsc_32.c
@@ -287,27 +287,14 @@ core_initcall(cpufreq_tsc);
/* 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 = {
diff --git a/arch/x86/kernel/tsc_64.c b/arch/x86/kernel/tsc_64.c
index 01fc9f0c39e..947554ddabb 100644
--- a/arch/x86/kernel/tsc_64.c
+++ b/arch/x86/kernel/tsc_64.c
@@ -11,7 +11,6 @@
#include <asm/hpet.h>
#include <asm/timex.h>
#include <asm/timer.h>
-#include <asm/vgtod.h>
static int notsc __initdata = 0;
@@ -291,34 +290,18 @@ int __init notsc_setup(char *s)
__setup("notsc", notsc_setup);
-static struct clocksource clocksource_tsc;
-/*
- * We compare the TSC to the cycle_last value in the clocksource
- * structure to avoid a nasty time-warp. This can be observed in a
- * very small window right after one CPU updated cycle_last under
- * xtime/vsyscall_gtod 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.
- */
+/* clock source code: */
static cycle_t read_tsc(void)
{
cycle_t ret = (cycle_t)get_cycles();
-
- return ret >= clocksource_tsc.cycle_last ?
- ret : clocksource_tsc.cycle_last;
+ return ret;
}
static cycle_t __vsyscall_fn vread_tsc(void)
{
cycle_t ret = (cycle_t)vget_cycles();
-
- return ret >= __vsyscall_gtod_data.clock.cycle_last ?
- ret : __vsyscall_gtod_data.clock.cycle_last;
+ return ret;
}
static struct clocksource clocksource_tsc = {