gcc_builtin_atomic_cas.c

/**
 * Strong version of atomic compare-and-swap
 * @p           pointer to cas with
 * @o           old value
 * @n           new value
 * @return      true if success  false o.w.
 * see: http://donghao.org/2015/01/30/128bit-atomic-operation-in-arm64
 *
 * NOTE: GCC-compatible available only
 */
#define atomic_cas(p, o, n) ({  \
    __typeof(*(p)) t = (o);     \
    __atomic_compare_exchange_n(p, &t, n, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); \
})

static int __k = 0;
#define spin_lock()     while (!atomic_cas(&__k, 0, 1)) continue
#define spin_unlock()   {               \
    int ok = atomic_cas(&__k, 1, 0);    \
    assert(ok);                         \
}