percpu: make PER_CPU_BASE_SECTION overridable by arches

Impact: bug fix

IA-64 needs to put percpu data in the seperate section even on UP.
Fixes regression caused by "percpu: refactor percpu.h"
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/ia64/include/asm/percpu.h

@@ -27,12 +27,12 @@ extern void *per_cpu_init(void);
 
 #else /* ! SMP */
 
-#define PER_CPU_ATTRIBUTES	__attribute__((__section__(".data.percpu")))
-
 #define per_cpu_init()				(__phys_per_cpu_start)
 
 #endif	/* SMP */
 
+#define PER_CPU_BASE_SECTION ".data.percpu"
+
 /*
  * Be extremely careful when taking the address of this variable!  Due to virtual
  * remapping, it is different from the canonical address returned by __get_cpu_var(var)!

include/linux/percpu.h

@@ -8,8 +8,15 @@
 
 #include <asm/percpu.h>
 
+#ifndef PER_CPU_BASE_SECTION
 #ifdef CONFIG_SMP
 #define PER_CPU_BASE_SECTION ".data.percpu"
+#else
+#define PER_CPU_BASE_SECTION ".data"
+#endif
+#endif
+
+#ifdef CONFIG_SMP
 
 #ifdef MODULE
 #define PER_CPU_SHARED_ALIGNED_SECTION ""
@@ -20,7 +27,6 @@
 
 #else
 
-#define PER_CPU_BASE_SECTION ".data"
 #define PER_CPU_SHARED_ALIGNED_SECTION ""
 #define PER_CPU_FIRST_SECTION ""