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-rw-r--r--arch/x86/kernel/tsc_32.c18
1 files changed, 8 insertions, 10 deletions
diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index 068759db63d..65b70637ad9 100644
--- a/arch/x86/kernel/tsc_32.c
+++ b/arch/x86/kernel/tsc_32.c
@@ -14,7 +14,10 @@
#include "mach_timer.h"
-static int tsc_disabled;
+/* native_sched_clock() is called before tsc_init(), so
+ we must start with the TSC soft disabled to prevent
+ erroneous rdtsc usage on !cpu_has_tsc processors */
+static int tsc_disabled = -1;
/*
* On some systems the TSC frequency does not
@@ -402,25 +405,20 @@ void __init tsc_init(void)
{
int cpu;
- if (!cpu_has_tsc || tsc_disabled) {
- /* Disable the TSC in case of !cpu_has_tsc */
- tsc_disabled = 1;
+ if (!cpu_has_tsc || tsc_disabled > 0)
return;
- }
cpu_khz = calculate_cpu_khz();
tsc_khz = cpu_khz;
if (!cpu_khz) {
mark_tsc_unstable("could not calculate TSC khz");
- /*
- * We need to disable the TSC completely in this case
- * to prevent sched_clock() from using it.
- */
- tsc_disabled = 1;
return;
}
+ /* now allow native_sched_clock() to use rdtsc */
+ tsc_disabled = 0;
+
printk("Detected %lu.%03lu MHz processor.\n",
(unsigned long)cpu_khz / 1000,
(unsigned long)cpu_khz % 1000);