---

yaml
---
r: 98291
b: refs/heads/master
c: df17b1d
h: refs/heads/master
i:
  98289: da8f5ce
  98287: 46b891d
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 75118a82e21cafb4a82b53bb85d1c7689787e046
+refs/heads/master: df17b1d990fc214f033c5588e58216ec941591e0

trunk/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);