Re: Ada and Unix--Blocked Tasks

[torolab4.vnet.ibm.com!jrussell@ucbvax.Berkeley.EDU]

Mike Feldman asks if any vendors map Ada tasks onto OS processes.
The IBM compiler for MVS has a pragma, OS_TASK, that does this for a
task or task type, and some form parameters that control
synchronous/asynchronous I/O.  (This is the same compiler Bob Kitzberger
mentioned.)  People who want to do real-timish things typically use the
pragma, because MVS task scheduling is pretty fair.  There are some
additional hooks into MVS tasking, such as a priority for MVS subtasks
distinct from the Ada priority, and ways to minimize the overhead of OS
task creation/termination.

The same pragma is part of the IBM RISC System/6000 compiler, using
the AIX shared memory features.

The approach does have some possible disadvantages, like more expensive
context switching, but people who need the extra capability are generally
positive.

John
(Representing myself only.)