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 ([email protected]) 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 9d55b9923a1b7ea8193b8875c57ec940dc2ff027.
>
>     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 <[email protected]>
Acked-by: Linus Torvalds <[email protected]>
CC: Linus Torvalds <[email protected]>
CC: H. Peter Anvin <[email protected]>
CC: Jeremy Fitzhardinge <[email protected]>
CC: Roland McGrath <[email protected]>
CC: Ingo Molnar <[email protected]>
Cc: Steven Rostedt <[email protected]>
CC: Steven Rostedt <[email protected]>
CC: Thomas Gleixner <[email protected]>
CC: Peter Zijlstra <[email protected]>
CC: Andrew Morton <[email protected]>
CC: David Miller <[email protected]>
CC: Ulrich Drepper <[email protected]>
CC: Rusty Russell <[email protected]>
CC: Gregory Haskins <[email protected]>
CC: Arnaldo Carvalho de Melo <[email protected]>
CC: "Luis Claudio R. Goncalves" <[email protected]>
CC: Clark Williams <[email protected]>
CC: Christoph Lameter <[email protected]>
CC: Andi Kleen <[email protected]>
CC: Harvey Harrison <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>

diff --git a/include/asm-x86/spinlock.h b/include/asm-x86/spinlock.h
index 4f9a9861799ac648d406856a8a5ed1881e678a25..0b4d59a93d2328500d91e26268298e1468456c25 100644 (file)
--- a/include/asm-x86/spinlock.h
+++ b/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"