/*

* myatomic.h -- support for atomic action (compare and swap)

*/

/* Atomically store NEWVAL in *MEM if *MEM is equal to OLDVAL and set eqz;

o/w clear eqz. Always return the old *MEM value.

The conditional atomic swap is performed if the return value == OLDVAL. */

#ifdef i386

# define __arch_compare_and_exchange_val_32_acq(mem, newval, oldval) \

({ __typeof (*mem) ret; \

__asm __volatile ("lock\n" "cmpxchgl %2, %1\n" \

: "=a" (ret), "=m" (*mem) \

: "r" (newval), "m" (*mem), "0" (oldval)); \

ret; })

# define compare_and_swap(mem, newval, oldval) \

__arch_compare_and_exchange_val_32_acq(mem, newval, oldval)

#else

# define __arch_compare_and_exchange_val_64_acq(mem, newval, oldval) \

({ __typeof (*mem) ret; \

__asm __volatile ("lock\n" "cmpxchgq %q2, %1\n" \

: "=a" (ret), "=m" (*mem) \

: "r" ((long int) (newval)), "m" (*mem), \

"0" ((long int) (oldval))); \

ret; })

# define compare_and_swap(mem, newval, oldval) \

__arch_compare_and_exchange_val_64_acq(mem, newval, oldval)

#endif