xchg

 1cat <<EOF
 2/**
 3 * ${class}${atomicname}() - atomic exchange with ${desc_order} ordering
 4 * @v: pointer to ${atomic}_t
 5 * @new: ${int} value to assign
 6 *
 7 * Atomically updates @v to @new with ${desc_order} ordering.
 8 *
 9 * ${desc_noinstr}
10 *
11 * Return: The original value of @v.
12 */
13EOF