2016-09-25 Kernel Threads and VT100 Console

The Ring 3 test from yesterday is useful and proves the TSS, but the rest of my OS is not quite set up yet to handle everything from process space with system calls and protected memory and the like.  What I really need is a way to run multiple tasks that are within kernel space.  What I need is KERNEL THREADS!

Because I already have much of a window manager in place, I made a quick change to the kernel main function so that instead of just opening a window for the console, it opens two more windows.  My test case is then a couple of functions which write characters into those other windows with a delay of of a few thousand nops, which will then get set to run as separate threads.

The method signature for the function to create a kernel thread looks like this
int32 process_kernelThreadStart( void* pThreadStart, size_t pStackSize, int32_t pParamCount, ... );
It allocates a stack for the thread and copies the parameters from its own stack into the thread stack it just allocated.  It also writes the address of a termination function to the stack so that if the thread function ever exits, it "returns" to termination function is called which collects the return value and terminates that thread.

2016-09-24 More Multitasking

A significant feature of many operating systems is the ability to multi-task.  You may be running Calculator and Sound Recorder and Wordpad and Sticky Notes and Doom and Paint and Command Prompt and Clippy, but they aren't actually running at the same time in the processor.  Instead, the processor is very quickly switching between them (with each running for maybe a few microseconds at a time) to make it appear if they are happening at once.

My multitasking system will be what is called pre-emptive multitasking, which is where the OS uses interrupts to pause the running programme in order to switch to the next programme.  This means that the programmes can be written as if they're the only programme on the system, the kernel takes care of the heavy lifting, and the programmes aren't usually aware that they were even interrupted.

Before I could design the multitasking system (or even fully understand a lot of the tutorials and articles on designing a multitasking OS) I had to go back and do a lot more research to get a solid footing in the concepts (hence the confused previous post).