- u32 old = (sem->count & 0xffff0000) | (u32) __old;
- u32 new = (old & 0xffff0000) | (u32) __new;
- u32 prev;
-
-again:
- __asm__ __volatile__("cas [%2], %3, %0\n\t"
- "membar #StoreLoad | #StoreStore"
- : "=&r" (prev)
- : "0" (new), "r" (sem), "r" (old)
- : "memory");
-
- /* To give the same semantics as x86 cmpxchgw, keep trying
- * if only the upper 16-bits changed.
- */
- if (prev != old &&
- ((prev & 0xffff) == (old & 0xffff)))
- goto again;
-
- return prev & 0xffff;