x86: move stack_start to smp.h

voyager would conflict with it, but the types are ultimately
compatible. So remove the extern definition from voyager_smp.c
in favour of the common one

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/smpboot_32.c

@@ -257,12 +257,6 @@ void __devinit initialize_secondary(void)
 		:"m" (current->thread.sp),"m" (current->thread.ip));
 }
 
-/* Static state in head.S used to set up a CPU */
-extern struct {
-	void * sp;
-	unsigned short ss;
-} stack_start;
-
 static inline void __inquire_remote_apic(int apicid)
 {
 	unsigned i, regs[] = { APIC_ID >> 4, APIC_LVR >> 4, APIC_SPIV >> 4 };

arch/x86/mach-voyager/voyager_smp.c

@@ -520,13 +520,6 @@ static void __init do_boot_cpu(__u8 cpu)
 	    & ~(voyager_extended_vic_processors
 		& voyager_allowed_boot_processors);
 
-	/* This is an area in head.S which was used to set up the
-	 * initial kernel stack.  We need to alter this to give the
-	 * booting CPU a new stack (taken from its idle process) */
-	extern struct {
-		__u8 *sp;
-		unsigned short ss;
-	} stack_start;
 	/* This is the format of the CPI IDT gate (in real mode) which
 	 * we're hijacking to boot the CPU */
 	union IDTFormat {

include/asm-x86/smp.h

@@ -28,6 +28,13 @@ extern const unsigned char trampoline_data [];
 extern const unsigned char trampoline_end  [];
 extern unsigned char *trampoline_base;
 
+/* Static state in head.S used to set up a CPU */
+extern struct {
+	void *sp;
+	unsigned short ss;
+} stack_start;
+
+
 struct smp_ops {
 	void (*smp_prepare_boot_cpu)(void);
 	void (*smp_prepare_cpus)(unsigned max_cpus);