suspicious code in ioapic locking

[Stephen Degler <sdegler%degler.net@localhost>]

The apic handling routines embedded in the macros in vector.S come from 
i82093reg.h, and operate on struct pic (sys/x86/include/pic.h).  The 
__cpu_simple_lock_t in the struct pic is now a byte, so the code is 
wrong.  This doesn't seem to break anything, probably due to structure 
padding.  The following patch corrects the ioapic code.  Another 
approach would be to rearrange the register usage so that the simple 
lock routines could be called directly, but this would be more 
involved.  In the patch below, I used %bl because %rbx is blown away in 
the macros anyway.

Let me know if you think I should commit this.

skd

Index: sys/arch/amd64/include/i82093reg.h
===================================================================
RCS file: /cvsroot/src/sys/arch/amd64/include/i82093reg.h,v
retrieving revision 1.3
diff -u -u -r1.3 i82093reg.h
--- sys/arch/amd64/include/i82093reg.h  11 May 2003 15:46:57 -0000      1.3
+++ sys/arch/amd64/include/i82093reg.h  23 Apr 2008 04:58:48 -0000
@@ -14,14 +14,13 @@
 #ifdef MULTIPROCESSOR
 
 #define ioapic_asm_lock(num) \
-       movl    $1,%esi                                         ;\
+       movb    $1,%bl                                  ;       \
 77:                                                            \
-       xchgl   %esi,PIC_LOCK(%rdi)                             ;\
-       testl   %esi,%esi                                       ;\
+        cmpxchgb %bl,PIC_LOCK(%rdi)                    ;       \
        jne     77b
 
 #define ioapic_asm_unlock(num) \
-       movl    $0,PIC_LOCK(%rdi)
+       movb    $0,PIC_LOCK(%rdi)
        
 #else