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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>
This commit is contained in:
Linus Torvalds 2008-08-24 11:52:06 -07:00 committed by H. Peter Anvin
parent 8735728ef8
commit 060700b571
1 changed files with 4 additions and 0 deletions
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4
arch/x86/kernel/tsc.c
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@ -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;