x86: spinlock use LOCK_PREFIX

Since we are now using DS prefixes instead of NOP to remove LOCK
prefixes, there is no longer any problems with instruction boundaries
moving around.

* Linus Torvalds (torvalds@linux-foundation.org) wrote:
>
>
> On Thu, 14 Aug 2008, Mathieu Desnoyers wrote:
> >
> > Changing the 0x90 (single-byte nop) currently used into a 0x3E DS segment
> > override prefix should fix this issue. Since the default of the atomic
> > instructions is to use the DS segment anyway, it should not affect the
> > behavior.
>
> Ok, so I think this is an _excellent_ patch, but I'd like to also then use
> LOCK_PREFIX in include/asm-x86/futex.h.
>
> See commit 9d55b992.
>
>     Linus

Unless there a rationale for this, I think these be changed to LOCK_PREFIX
too.

grep "lock ;" include/asm-x86/spinlock.h
         "lock ; cmpxchgw %w1,%2\n\t"
  asm volatile("lock ; xaddl %0, %1\n"
         "lock ; cmpxchgl %1,%2\n\t"

Applies to 2.6.27-rc2.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: H. Peter Anvin <hpa@zytor.com>
CC: Jeremy Fitzhardinge <jeremy@goop.org>
CC: Roland McGrath <roland@redhat.com>
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Cc: Steven Rostedt <rostedt@goodmis.org>
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CC: Christoph Lameter <cl@linux-foundation.org>
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Signed-off-by: H. Peter Anvin <hpa@zytor.com>

include/asm-x86/spinlock.h

@@ -97,7 +97,7 @@ static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
 		     "jne 1f\n\t"
 		     "movw %w0,%w1\n\t"
 		     "incb %h1\n\t"
-		     "lock ; cmpxchgw %w1,%2\n\t"
+		     LOCK_PREFIX "cmpxchgw %w1,%2\n\t"
 		     "1:"
 		     "sete %b1\n\t"
 		     "movzbl %b1,%0\n\t"
@@ -135,7 +135,7 @@ static __always_inline void __ticket_spin_lock(raw_spinlock_t *lock)
 	int inc = 0x00010000;
 	int tmp;
 
-	asm volatile("lock ; xaddl %0, %1\n"
+	asm volatile(LOCK_PREFIX "xaddl %0, %1\n"
 		     "movzwl %w0, %2\n\t"
 		     "shrl $16, %0\n\t"
 		     "1:\t"
@@ -162,7 +162,7 @@ static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
 		     "cmpl %0,%1\n\t"
 		     "jne 1f\n\t"
 		     "addl $0x00010000, %1\n\t"
-		     "lock ; cmpxchgl %1,%2\n\t"
+		     LOCK_PREFIX "cmpxchgl %1,%2\n\t"
 		     "1:"
 		     "sete %b1\n\t"
 		     "movzbl %b1,%0\n\t"