i386: improve and correct inline asm memory constraints

Use "+m" rather than a combination of "=m" and "m" for improved clarity
and consistency.

This also fixes some inlines that incorrectly didn't tell the compiler
that they read the old value at all, potentially causing the compiler to
generate bogus code.  It appear that all of those potential bugs were
hidden by the use of extra "volatile" specifiers on the data structures
in question, though.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 8 deletions

diff --git a/include/asm-i386/local.h b/include/asm-i386/local.h
index 3b4998c51d08..12060e22f7e2 100644
--- a/include/asm-i386/local.h
+++ b/include/asm-i386/local.h
@@ -17,32 +17,30 @@ static __inline__ void local_inc(local_t *v)
 {
         __asm__ __volatile__(
                 "incl %0"
-                :"=m" (v->counter)
-                :"m" (v->counter));
+                :"+m" (v->counter));
 }
 
 static __inline__ void local_dec(local_t *v)
 {
         __asm__ __volatile__(
                 "decl %0"
-                :"=m" (v->counter)
-                :"m" (v->counter));
+                :"+m" (v->counter));
 }
 
 static __inline__ void local_add(long i, local_t *v)
 {
         __asm__ __volatile__(
                 "addl %1,%0"
-                :"=m" (v->counter)
-                :"ir" (i), "m" (v->counter));
+                :"+m" (v->counter)
+                :"ir" (i));
 }
 
 static __inline__ void local_sub(long i, local_t *v)
 {
         __asm__ __volatile__(
                 "subl %1,%0"
-                :"=m" (v->counter)
-                :"ir" (i), "m" (v->counter));
+                :"+m" (v->counter)
+                :"ir" (i));
 }
 
 /* On x86, these are no better than the atomic variants. */