  In the case of multi-threading as found in contemporary programming
languages, parallel processes are interleaved according to what is known as a
process-scheduling policy in the field of operating systems. In a previous
paper, we extend ACP with this form of interleaving. In the current paper, we
do so with the variant of ACP known as ACP$_\epsilon$. The choice of
ACP$_\epsilon$ stems from the need to cover more process-scheduling policies.
We show that a process-scheduling policy supporting mutual exclusion of
critical subprocesses is now covered.
