Implementing a Multitasking System

t0xic · Post by **t0xic** » Wed Dec 26, 2007 5:23 pm

Hey everyone! It's been awhile, but I decided to hop back into OS dev'ing for a little while. I left off after implementing paging/memory management into my kernel, and I was wondering if any of you have implemented a working software or hardware multitasking system, as I would like that to be the next goal for my little hobby.

I have worked on a hardware context switching system, but I cannot get it to work... back to google for now...

I am aware of the pros and cons of each system, and I would like to use software multitasking, but I can't find any good resources out on the web. Do any of you have any reliable resources/code that I could look at?

Thanks,
Michael

ucosty · Post by **ucosty** » Wed Dec 26, 2007 5:29 pm

Forget hardware multitasking. It's inflexible and only works on x86 chips in 32bit mode.

There is lots of info on this site and osdever.net. If you have any specific questions I can answer them as I have implemented a ring0/3 software task switcher.

lukem95 · Post by **lukem95** » Wed Dec 26, 2007 5:31 pm

Many people have done on this forum, i'd take a look at www.jamesmolloy.co.uk, as his tutorials are excellent and cover loading modules.. which is the first step to programs.

you then need ELF/COFF(-PE) (depending on format)relocation to successfully run the app.

i can't help with multi-tasking im afraid, as i have no idea myself, apart from that it involved using the GDT to create a TSS for each task.

ucosty · Post by **ucosty** » Wed Dec 26, 2007 5:34 pm

lukem_95 wrote:i can't help with multi-tasking im afraid, as i have no idea myself, apart from that it involved using the GDT to create a TSS for each task.

Thats only for hardware task switching. Software switching only requires one TSS per CPU (to store the Ring 0 ESP).

t0xic · Post by **t0xic** » Wed Dec 26, 2007 5:57 pm

Thanks for reminding me about osdever... Reading one of the tut's now

Thanks,

Michael