This is thrown for an illegal operation on an
AltingBarrier.
Description
Currently, there are the following causes:
-
different threads trying to operate on the same front-end;
-
attempt to use as a
Guard whilst resigned;
-
attempt to
sync whilst resigned;
-
attempt to
resign whilst resigned;
-
attempt to
enroll whilst enrolled;
-
attempt to
expand whilst resigned;
-
attempt to
contract whilst resigned;
-
attempt to
contract with an array
of front-ends not supplied by expand;
-
attempt to
mark whilst resigned (caused
by a process transfering a front-end in that state).