15.8.1 Specific Process Wait functions

For communication between processes, these are:

mailbox-read, process-wait-for-event and mailbox-wait-for-event.

For synchronization, these are:

condition-variable-wait and barrier-wait, also semaphore-acquire and semaphore-release.

For locking these are:

process-lock, process-exclusive-lock and process-sharing-lock.

For sleeping, these are:

cl:sleep and current-process-pause.