[PATCH] per_cpu: Fix cmpxchg_double() for !SMP

[Christoph Lameter]

cmpxchg_double() should only be provided for SMP. In the UP case
the GS register is not defined and the function will fail.

Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: torvalds@xxxxxxxxxxxxxxxxxxxx
Cc: tj@xxxxxxxxxx
Cc: npiggin@xxxxxxxxx
Cc: rientjes@xxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
LKML-Reference: <alpine.DEB.2.00.1103261440160.25375@xxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
 arch/x86/include/asm/percpu.h |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index a09e1f0..52330a4 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -507,6 +507,7 @@ do {									\
  * it in software.  The address used in the cmpxchg16 instruction must be
  * aligned to a 16 byte boundary.
  */
+#ifdef CONFIG_SMP
 #define percpu_cmpxchg16b_double(pcp1, o1, o2, n1, n2)			\
 ({									\
 	char __ret;							\
@@ -529,6 +530,7 @@ do {									\
 #define irqsafe_cpu_cmpxchg_double_8(pcp1, pcp2, o1, o2, n1, n2)	percpu_cmpxchg16b_double(pcp1, o1, o2, n1, n2)
 
 #endif
+#endif
 
 /* This is not atomic against other CPUs -- CPU preemption needs to be off */
 #define x86_test_and_clear_bit_percpu(bit, var)				\
--
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