linux-kernel - [PATCH] [3/45] x86: Separate checking of unsynchronized and unstable TSC

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Message-Id: <20070921204444.234A314EFF@wotan.suse.de>
Date:	Fri, 21 Sep 2007 22:44:44 +0200 (CEST)
From:	Andi Kleen <ak@...e.de>
To:	patches@...-64.org, linux-kernel@...r.kernel.org
Subject: [PATCH] [3/45] x86: Separate checking of unsynchronized and unstable TSC


Preparationary patch for the new sched/printk_clock()

Signed-off-by: Andi Kleen <ak@...e.de>

---
 arch/i386/kernel/tsc.c   |    9 ++++-----
 arch/x86_64/kernel/tsc.c |    5 +----
 2 files changed, 5 insertions(+), 9 deletions(-)

Index: linux/arch/i386/kernel/tsc.c
===================================================================
--- linux.orig/arch/i386/kernel/tsc.c
+++ linux/arch/i386/kernel/tsc.c
@@ -332,7 +332,7 @@ static struct dmi_system_id __initdata b
  */
 __cpuinit int unsynchronized_tsc(void)
 {
-	if (!cpu_has_tsc || tsc_unstable)
+	if (!cpu_has_tsc)
 		return 1;
 	/*
 	 * Intel systems are normally all synchronized.
@@ -341,9 +341,9 @@ __cpuinit int unsynchronized_tsc(void)
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
 		/* assume multi socket systems are not synchronized: */
 		if (num_possible_cpus() > 1)
-			tsc_unstable = 1;
+			return 1;
 	}
-	return tsc_unstable;
+	return 0;
 }
 
 /*
@@ -387,13 +387,12 @@ void __init tsc_init(void)
 	/* Check and install the TSC clocksource */
 	dmi_check_system(bad_tsc_dmi_table);
 
-	unsynchronized_tsc();
 	check_geode_tsc_reliable();
 	current_tsc_khz = tsc_khz;
 	clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
 							clocksource_tsc.shift);
 	/* lower the rating if we already know its unstable: */
-	if (check_tsc_unstable()) {
+	if (check_tsc_unstable() || unsynchronized_tsc()) {
 		clocksource_tsc.rating = 0;
 		clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
 	} else
Index: linux/arch/x86_64/kernel/tsc.c
===================================================================
--- linux.orig/arch/x86_64/kernel/tsc.c
+++ linux/arch/x86_64/kernel/tsc.c
@@ -124,9 +124,6 @@ core_initcall(cpufreq_tsc);
  */
 __cpuinit int unsynchronized_tsc(void)
 {
-	if (tsc_unstable)
-		return 1;
-
 #ifdef CONFIG_SMP
 	if (apic_is_clustered_box())
 		return 1;
@@ -199,7 +196,7 @@ void __init init_tsc_clocksource(void)
 	if (!notsc) {
 		clocksource_tsc.mult = clocksource_khz2mult(tsc_khz,
 							clocksource_tsc.shift);
-		if (check_tsc_unstable())
+		if (unsynchronized_tsc() || check_tsc_unstable())
 			clocksource_tsc.rating = 0;
 
 		clocksource_register(&clocksource_tsc);
-
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