From: Greg KH on
2.6.32-stable review patch. If anyone has any objections, please let us know.


From: Suresh Siddha <suresh.b.siddha(a)>

commit 472a474c6630efd195d3738339fd1bdc8aa3b1aa upstream.

Jan Grossmann reported kernel boot panic while booting SMP
kernel on his system with a single core cpu. SMP kernels call
enable_IR_x2apic() from native_smp_prepare_cpus() and on
platforms where the kernel doesn't find SMP configuration we
ended up again calling enable_IR_x2apic() from the
APIC_init_uniprocessor() call in the smp_sanity_check(). Thus
leading to kernel panic.

Don't call enable_IR_x2apic() and default_setup_apic_routing()
from APIC_init_uniprocessor() in CONFIG_SMP case.

NOTE: this kind of non-idempotent and assymetric initialization
sequence is rather fragile and unclean, we'll clean that up
in v2.6.35. This is the minimal fix for v2.6.34.

Reported-by: Jan.Grossmann(a)
Signed-off-by: Suresh Siddha <suresh.b.siddha(a)>
Cc: <jbarnes(a)>
Cc: <david.woodhouse(a)>
Cc: <weidong.han(a)>
Cc: <>
Cc: <Jan.Grossmann(a)>
LKML-Reference: <1270083887.7835.78.camel(a)>
Signed-off-by: Ingo Molnar <mingo(a)>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)>

arch/x86/kernel/apic/apic.c | 2 ++
1 file changed, 2 insertions(+)

--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1664,8 +1664,10 @@ int __init APIC_init_uniprocessor(void)

+#ifndef CONFIG_SMP


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