[PATCH] x86_64: Fix safe_smp_processor_id after genapic

[Andi Kleen <ak@muc.de>]

genapic broke early safe_smp_processor_id(), especially when you
got a WARN_ON or oops early it would loops forever in show_trace.
The reason was that the x86_cpu_to_apicid array wasn't correctly
initialized.

This patch fixes this by just testing for this case.


Orginally from James Cleverdon
Acked-by: Andi Kleen <ak@muc.de> 

Please apply ASAP

Index: linux/include/asm-x86_64/smp.h
===================================================================
--- linux.orig/include/asm-x86_64/smp.h	2004-10-28 11:32:15.%N +0200
+++ linux/include/asm-x86_64/smp.h	2004-10-29 01:30:29.%N +0200
@@ -104,6 +104,11 @@
 		if (x86_cpu_to_apicid[i] == apicid)
 			return i;
 
+	/* No entries in x86_cpu_to_apicid?  Either no MPS|ACPI,
+	 * or called too early.  Either way, we must be CPU 0. */
+      	if (x86_cpu_to_apicid[0] == BAD_APICID)
+		return 0;
+
 	return -1;
 }