From 060700b571717c997a2ea5e2049b848fa248ee13 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sun, 24 Aug 2008 11:52:06 -0700
Subject: [PATCH] x86: do not enable TSC notifier if we don't need it
Impact: crash on non-TSC-equipped CPUs
Don't enable the TSC notifier if we *either*:
1. don't have a CPU, or
2. have a CPU with constant TSC.
In either of those cases, the notifier is either damaging (1) or useless(2).
From: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---
arch/x86/kernel/tsc.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 46af71676738e..9bed5cae4bdcc 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -325,6 +325,10 @@ static struct notifier_block time_cpufreq_notifier_block = {
static int __init cpufreq_tsc(void)
{
+ if (!cpu_has_tsc)
+ return 0;
+ if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
+ return 0;
cpufreq_register_notifier(&time_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
return 0;
--
2.30.2