fix powerpc atomic compare-and-swap function

previous version did not compare at all; it was just a fancy atomic
write. untested. further atomic fixes may be needed.

diff --git a/arch/powerpc/atomic.h b/arch/powerpc/atomic.h
index a83764d..4a47064 100644 (file)
--- a/arch/powerpc/atomic.h
+++ b/arch/powerpc/atomic.h
@@ -25,12 +25,13 @@ static inline int a_ctz_64(uint64_t x)
 
 static inline int a_cas(volatile int *p, int t, int s)
 {
-
-       __asm__( "1: lwarx 10, 0, %1\n"
-                 "   stwcx. %3, 0, %1\n"
-                 "   bne- 1b\n"
-                 "   mr %0, 10\n"
-               : "=r"(t) : "r"(p), "r"(t), "r"(s) : "memory" );
+       __asm__("1:     lwarx %0, 0, %1\n"
+               "       cmpw %0, %2\n"
+               "       bne 1f\n"
+               "       stwcx. %3, 0, %1\n"
+               "       bne- 1b\n"
+               "1:     \n"
+               : "=&r"(t) : "r"(p), "r"(t), "r"(s) : "cc", "memory" );
         return t;
 }