From: "Matthias Paul" Organization: IBH, RWTH-Aachen To: opendos AT mail DOT tacoma DOT net Date: Thu, 13 Mar 1997 17:45:33 GMT+0100 Subject: Re: [opendos] prospective user questions Reply-to: Matthias DOT Paul AT post DOT rwth-aachen DOT de Message-ID: <37AAD6B3A6E@ibh.rwth-aachen.de> Sender: owner-opendos AT mail DOT tacoma DOT net Precedence: bulk On Tue, 11 Mar 1997 Colin W. Glenn replied: > > > Does it allow for controlling applications which do not give up > > > their time slice on their own? > > Yes, it's preemptive multitasking! That's one of the major > > advantages compared to Windows 3.xx/95. > > Does this mean you can shoot and kill a task without crashing the > rest of the system? Yes, the OpenDOS multitasking kernel can do that - at least in theory, since each domain runs in a virtual DOS machine, and on closing tasks, the kernel will try to free remaining resources used by that task. In practice, it can't do that under all circumstances, because it needs to detect, that resources were actually allocated by *that* domain and freeing them does not interfer with other system tasks, especially in global memory areas. There are scenarios, were this cannot be determined, and other tasks could have be affected. Of course, local and instanced data will be lost, including open files, which have not been flushed before the shutdown. However, all that has nothing to do with pre-emptive or cooperative multitasking, but with virtualization. In short words, the problem with cooperative multitasking is, that if an application fails, it may hang the whole system, if it does not give back the token, and the scheduler will wait forever to get it back. In an pre-emptive system, the scheduler always has the ability, to get the token back and suspend the task. Bye, Matthias ------------------------------------------------------------------ Matthias Paul ! My eMail address has changed. For some time ! Ubierstrasse 28 ! mails to former ! D-50321 BRUEHL ! will be forwarded to the new address. ! eMail: WWW : URL: http://www.rhrz.uni-bonn.de/~uzs180/mpdokger.html ------------------------------------------------------------------