From: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 18 May 2008 20:17:59 +0000 (+0200)
Subject: x86: disable TSC for sched_clock() when calibration failed
X-Git-Tag: v2.6.26-rc4~11^2~5
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=74dc51a3de06aa516e3b9fdc4017b2aeb38bf44b;p=linux-2.6-omap-h63xx.git

x86: disable TSC for sched_clock() when calibration failed

When the TSC calibration fails then TSC is still used in
sched_clock(). Disable it completely in that case.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org
---

diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index b087d691f16..068759db63d 100644
--- a/arch/x86/kernel/tsc_32.c
+++ b/arch/x86/kernel/tsc_32.c
@@ -413,6 +413,11 @@ void __init tsc_init(void)
 
 	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;
 	}