Since Dos can have multiple ways of multitasking (it could e.g. also plug in
to DV or Win3.x or TopView via int 2FH etc) this model seems advisable to me.
I assume you are implementing a basic fixed timeslicer? What are you going
to use it for btw? This because DV/X (which is free nowadays) afaik gives
you preemptive scheduling on Dos.
DV is not suitable since it is a multi-tasker but does not have a
multithreading library (at least I don't think so). I want to implement
TThread so that I can have threads running in the background. Basically
the threading system will have:
- Implement full TThread functionality.
- Protection of int21. When a thread is using int21, other threads that
try to use it are blocked until the first thread releases int21. I will
probably make keyboard reads non-blocking (of int21) as well.
- When the first thread is created, the main application becomes a
thread as well. (ei. multi-treading is enabled). The main thread can not
be deleted.
I already have a good threading library for Watcom C, but it is only for
systems that don't use floating point since I don't know how to save and
restore the floating point unit. I will need to do this for FPC, so if
someone knows how to save and restore the FPU, I would apreciate the
help. Ideally I could also discover (via an exception on first FPU
usage?) if a thread needs to save/restore the FPU. This would greatly
speed up swapping of FPU-free threads.
Regards,
Andreas
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