The function process-arrest-reasons
returns a list of the reasons why a Lisp process has stopped. A process is inactive if it has any arrest reasons.
Use of (setf mp:process-arrest-reasons)
is deprecated. You should use process-stop instead. If you set the arrest reasons of the current process, this causes the current process to stop immediately, before returning from mp:process-arrest-reasons
(like process-stop).
The immediate stopping behavior of (setf mp:process-arrest-reasons)
is different from LispWorks 5.0 and previous versions.
LispWorks User Guide and Reference Manual - 20 Sep 2017