9.7.3 Conditional Entry Calls
issues an entry call that is then cancelled if it is not selected immediately
(or if a requeue-with-abort of the call is not selected immediately).
A procedure call may appear rather than an entry call for cases where
the procedure might be implemented by an entry.
40 A conditional_entry_call
may briefly increase the Count attribute of the entry, even if the conditional
call is not selected.
Example of a conditional
procedure Spin(R : in Resource) is
null; -- busy waiting