Multitasking
Posted: 17 Feb 2024, 13:11
In an attempt to improve the virtual interrupt system (the one that diverts the vCPU whenever frameCount wraps over), I wrote native instructions to save and restore the full vCPU context and arranged a way to have this done automatically when a virtual interrupt occurs. The rationale is explained in https://forum.gigatron.io/viewtopic.php?p=4169#p4169 and the final details are documented in https://github.com/lb3361/gigatron-rom/ ... interrupts. It took several rewrites to have a setup that is good enough to hit one of Marcel's long-term ideas : task switching.
There is now a proof of concept in https://github.com/lb3361/gigatron-lcc/ ... ff/threads.
The C program ’threads_test.c’ spawns two threads, one that computes prime numbers, another one that draws a maze in the bottom of the screen. Then it goes in a loop that prints the elapsed time until the prime numbers thread terminates. This program creates and manages threads using a small library with prototypes in ’threads.h’ and implementation in ’threads.s’. To make this work, I had to make changes in both the dev7 rom and in the compiler. It was also necessary to use a mutex to print things because the glcc library is not reentrant at this point.
To run the attached gt1 file, you need a very recent version of the dev7 rom, or you can also try it in www.gigatron128k.com using the "Load GT1" button.
There is now a proof of concept in https://github.com/lb3361/gigatron-lcc/ ... ff/threads.
The C program ’threads_test.c’ spawns two threads, one that computes prime numbers, another one that draws a maze in the bottom of the screen. Then it goes in a loop that prints the elapsed time until the prime numbers thread terminates. This program creates and manages threads using a small library with prototypes in ’threads.h’ and implementation in ’threads.s’. To make this work, I had to make changes in both the dev7 rom and in the compiler. It was also necessary to use a mutex to print things because the glcc library is not reentrant at this point.
Code: Select all
int main(void)
{
gt_start(&th1, th1s, sizeof(th1s), run_primes, 0);
gt_start(&th2, th2s, sizeof(th1s), run_maze, 0);
run_elapsed(0);
safe_cputs(1, 9, LIGHTMAGENTA, "Finished!");
return 0;
}
- threads_test.png (53.35 KiB) Viewed 1401 times