1 files changed, 10 insertions, 14 deletions

diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index 068759db63dd..774a5a83c296 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
@@ -283,7 +286,6 @@ core_initcall(cpufreq_tsc);
 
 /* clock source code */
 
-static unsigned long current_tsc_khz;
 static struct clocksource clocksource_tsc;
 
 /*
@@ -402,25 +404,20 @@ 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);
@@ -441,9 +438,8 @@ void __init tsc_init(void)
 
         unsynchronized_tsc();
         check_geode_tsc_reliable();
-        current_tsc_khz = tsc_khz;
-        clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
-                                                        clocksource_tsc.shift);
+        clocksource_tsc.mult = clocksource_khz2mult(tsc_khz,
+                                                    clocksource_tsc.shift);
         /* lower the rating if we already know its unstable: */
         if (check_tsc_unstable()) {
                 clocksource_tsc.rating = 0;