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x86, AMD: Fix stale cpuid4_info shared_map data in shared_cpu_map cpumasks

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The per_cpu cpuid4_info shared_map can contain stale data when CPUs are added
and removed.

The stale data can lead to a NULL pointer derefernce panic on a remove of a
CPU that has had siblings previously removed.

This patch resolves the panic by verifying a cpu is actually online before
adding it to the shared_cpu_map, only examining cpus that are part of
the same lower level cache, and by updating other siblings lowest level cache
maps when a cpu is added.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
LKML-Reference: <20091209183336.17855.98708.sendpatchset@prarit.bos.redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Prarit Bhargava 2009-12-09 13:36:45 -05:00 committed by H. Peter Anvin
parent 9cf7826743
commit ebb682f522
1 changed files with 7 additions and 6 deletions
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13
arch/x86/kernel/cpu/intel_cacheinfo.c
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@ -507,18 +507,19 @@ static void __cpuinit cache_shared_cpu_map_setup(unsigned int cpu, int index)
{
struct _cpuid4_info *this_leaf, *sibling_leaf;
unsigned long num_threads_sharing;
int index_msb, i;
int index_msb, i, sibling;
struct cpuinfo_x86 *c = &cpu_data(cpu);
if ((index == 3) && (c->x86_vendor == X86_VENDOR_AMD)) {
struct cpuinfo_x86 *d;
for_each_online_cpu(i) {
for_each_cpu(i, c->llc_shared_map) {
if (!per_cpu(cpuid4_info, i))
continue;
d = &cpu_data(i);
this_leaf = CPUID4_INFO_IDX(i, index);
cpumask_copy(to_cpumask(this_leaf->shared_cpu_map),
d->llc_shared_map);
for_each_cpu(sibling, c->llc_shared_map) {
if (!cpu_online(sibling))
continue;
set_bit(sibling, this_leaf->shared_cpu_map);
}
}
return;
}