cmpxchg

 1cat <<EOF
 2/**
 3 * ${class}${atomicname}() - atomic compare and exchange with ${desc_order} ordering
 4 * @v: pointer to ${atomic}_t
 5 * @old: ${int} value to compare with
 6 * @new: ${int} value to assign
 7 *
 8 * If (@v == @old), atomically updates @v to @new with ${desc_order} ordering.
 9 * Otherwise, @v is not modified and relaxed ordering is provided.
10 *
11 * ${desc_noinstr}
12 *
13 * Return: The original value of @v.
14 */
15EOF