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From: Greg KH on 30 Mar 2010 20:40
2.6.31-stable review patch. If anyone has any objections, please let us know.

------------------

From: Thomas Renninger <trenn(a)suse.de>

commit 557a701c16553b0b691dbb64ef30361115a80f64 upstream.

Easy fix for a regression introduced in 2.6.31.

On managed CPUs the cpufreq.c core will call driver->exit(cpu) on the
managed cpus and powernow_k8 will free the core's data.

Later driver->get(cpu) function might get called trying to read out the
current freq of a managed cpu and the NULL pointer check does not work on
the freed object -> better set it to NULL.

->get() is unsigned and must return 0 as invalid frequency.

Reference:
http://bugzilla.kernel.org/show_bug.cgi?id=14391

Signed-off-by: Thomas Renninger <trenn(a)suse.de>
Tested-by: Michal Schmidt <mschmidt(a)redhat.com>
Signed-off-by: Dave Jones <davej(a)redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>

---
arch/x86/kernel/cpu/cpufreq/powernow-k8.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
+++ b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
@@ -1372,6 +1372,7 @@ static int __devexit powernowk8_cpu_exit

kfree(data->powernow_table);
kfree(data);
+ per_cpu(powernow_data, pol->cpu) = NULL;

return 0;
}
@@ -1391,7 +1392,7 @@ static unsigned int powernowk8_get(unsig
int err;

if (!data)
- return -EINVAL;
+ return 0;

smp_call_function_single(cpu, query_values_on_cpu, &err, true);
if (err)


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