[PATCH] x86: Log reason why TSC was marked unstable

Change mark_tsc_unstable() so it takes a string argument, which holds the
reason the TSC was marked unstable.

This is then displayed the first time mark_tsc_unstable is called.

This should help us better debug why the TSC was marked unstable on certain
systems and allow us to make sure we're not being overly paranoid when
throwing out this troublesome clocksource.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>

5 files changed, 9 insertions, 7 deletions

diff --git a/arch/i386/kernel/cpu/cyrix.c b/arch/i386/kernel/cpu/cyrix.c
index f0badfdd4e4..e77f8e1cf7a 100644
--- a/arch/i386/kernel/cpu/cyrix.c
+++ b/arch/i386/kernel/cpu/cyrix.c
@@ -279,7 +279,7 @@ static void __cpuinit init_cyrix(struct cpuinfo_x86 *c)
 		 */  
 		if (vendor == PCI_VENDOR_ID_CYRIX &&
 	 (device == PCI_DEVICE_ID_CYRIX_5510 || device == PCI_DEVICE_ID_CYRIX_5520))
-			mark_tsc_unstable();
+			mark_tsc_unstable("cyrix 5510/5520 detected");
 	}
 #endif
 		c->x86_cache_size=16;	/* Yep 16K integrated cache thats it */
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index 6cb8f533673..755209dc93e 100644
--- a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -233,7 +233,7 @@ time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data)
 				 * TSC based sched_clock turns
 				 * to junk w/ cpufreq
 				 */
-				mark_tsc_unstable();
+				mark_tsc_unstable("cpufreq changes");
 			}
 		}
 	}
@@ -281,11 +281,12 @@ static struct clocksource clocksource_tsc = {
 				  CLOCK_SOURCE_MUST_VERIFY,
 };
 
-void mark_tsc_unstable(void)
+void mark_tsc_unstable(char *reason)
 {
 	if (!tsc_unstable) {
 		tsc_unstable = 1;
 		tsc_enabled = 0;
+		printk("Marking TSC unstable due to: %s.\n", reason);
 		/* Can be called before registration */
 		if (clocksource_tsc.mult)
 			clocksource_change_rating(&clocksource_tsc, 0);
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 5f862e216a4..91c9066a380 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -397,7 +397,7 @@ void __init time_init(void)
 		cpu_khz = tsc_calibrate_cpu_khz();
 
 	if (unsynchronized_tsc())
-		mark_tsc_unstable();
+		mark_tsc_unstable("TSCs unsynchronized");
 
 	if (cpu_has(&boot_cpu_data, X86_FEATURE_RDTSCP))
 		vgetcpu_mode = VGETCPU_RDTSCP;
diff --git a/arch/x86_64/kernel/tsc.c b/arch/x86_64/kernel/tsc.c
index 5c84992c676..48f9a8e6aa9 100644
--- a/arch/x86_64/kernel/tsc.c
+++ b/arch/x86_64/kernel/tsc.c
@@ -111,7 +111,7 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
 
 		tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new);
 		if (!(freq->flags & CPUFREQ_CONST_LOOPS))
-			mark_tsc_unstable();
+			mark_tsc_unstable("cpufreq changes");
 	}
 
 	set_cyc2ns_scale(tsc_khz_ref);
@@ -199,10 +199,11 @@ static struct clocksource clocksource_tsc = {
 	.vread			= vread_tsc,
 };
 
-void mark_tsc_unstable(void)
+void mark_tsc_unstable(char *reason)
 {
 	if (!tsc_unstable) {
 		tsc_unstable = 1;
+		printk("Marking TSC unstable due to %s\n", reason);
 		/* Change only the rating, when not registered */
 		if (clocksource_tsc.mult)
 			clocksource_change_rating(&clocksource_tsc, 0);
diff --git a/arch/x86_64/kernel/tsc_sync.c b/arch/x86_64/kernel/tsc_sync.c
index 72d444dede9..355f5f506c8 100644
--- a/arch/x86_64/kernel/tsc_sync.c
+++ b/arch/x86_64/kernel/tsc_sync.c
@@ -138,7 +138,7 @@ void __cpuinit check_tsc_sync_source(int cpu)
 		printk("\n");
 		printk(KERN_WARNING "Measured %Ld cycles TSC warp between CPUs,"
 				    " turning off TSC clock.\n", max_warp);
-		mark_tsc_unstable();
+		mark_tsc_unstable("check_tsc_sync_source failed");
 		nr_warps = 0;
 		max_warp = 0;
 		last_tsc = 0;