dec_if_positive

 1cat <<EOF
 2	${int} dec, c = raw_${atomic}_read(v);
 3
 4	do {
 5		dec = c - 1;
 6		if (unlikely(dec < 0))
 7			break;
 8	} while (!raw_${atomic}_try_cmpxchg(v, &c, dec));
 9
10	return dec;
11EOF