klamer@mi.eltn.utwente.nl (Klamer Schutte) (05/03/91)
When designing a pty driver for minix i encounter the following problem:
I want to add a kernel task to minix (st) 1.5.10 which can give on 1 TTY_WRITE
message from the FS up to 3 messages back to FS (1 for the succeeded write;
1 for the echoed output and 1 for the pty output).
All three messages will cause FS on his turn to activate a different process
(We don't have a select(2) system call :-().
My question is now: Does three (or more common, two) messages sended to FS
result in one or more lost messages? If so, how to circumvent this problem?
(I see two solutions: the first one is let the next message be sended at a
later time (by a clock interrupt). But this introduces a delay which should
not be neccessary. The other way you need to tell FS in the answer that it
has to retry the kernel tasks as soon as it has started the user process
asking for the I/O. But that seems a dirty hack to me.
So, minix gurus: what is (the|a) solution?
Klamer
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Klamer Schutte
Faculty of electrical engineering -- University of Twente, The Netherlands
klamer@mi.eltn.utwente.nl {backbone}!mcsun!mi.eltn.utwente.nl!klamer