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    // the stack size: 4k.   move the pointer to the end
    uint32_t *stack = kmalloc(0x400) + 0x3F0;

    //0x567 is arbitrarily
    thread_t *t = create_thread(&fn, (void*)0x567, stack);
    init_scheduler(t);
    uint32_t *stack1 = kmalloc(0x400) + 0x3F0;
    thread_t *t1 = create_thread(&fn1, (void*)0x567, stack1);

    init_timer(20);
    asm volatile("sti");
	for(;;) ;

Code: Select all

thread_t *create_thread(int (*fn)(void*), void *arg, uint32_t *stack)
{
    thread_t *thread = (thread_t*)kmalloc(sizeof(thread_t));
    memset(thread, 0, sizeof(thread_t));
    thread->id = next_tid++;

    *--stack = (uint32_t)arg;
    *--stack = (uint32_t)&thread_exit;
    *--stack = (uint32_t)fn;

    thread->esp = (uint32_t)stack;
    thread->ebp = 0;
    thread->eflags = 0x200;
    thread_is_ready(thread);
    return thread;
}

Code: Select all

void schedule()
{
    if(!ready_queue) return;        //deque empty

    //iterator through the ready queue to the end
    thread_list_t *iterator = ready_queue;
    while(iterator->next)
        iterator = iterator->next;

    //add the old thread to the end of the deque, and remove it from the start
    iterator->next = current_thread;
    current_thread->next = 0;
    thread_list_t *new_thread = ready_queue;
    ready_queue = ready_queue->next;

    //switch to the new thread.
    switch_thread(new_thread);
}

Code: Select all

static void timer_callback(registers_t *regs)
{
    tick++;
//    if(tick%20)
//        return;

    monitor_write("Tick: ");
    monitor_write_dec(tick);
    monitor_write("\n");
    schedule();
}

Code: Select all

int fn(void *arg)
{
    for(;;)
    {
        monitor_write("a");
    }

    return 0;
}

int fn1(void *arg)
{
    for(;;)
    {
        monitor_write("b");
    }
    return 0;
}

Code: Select all

switch_thread:
    mov eax, [current_thread]   ;assign the pointer address to eax
    mov eax, [eax]

    mov [eax+0],  esp           ; save
    mov [eax+4],  ebp
    mov [eax+8],  ebx
    mov [eax+12], esi
    mov [eax+16], edi

    pushf                       ; update eflags
    pop ecx
    mov [eax+20], ecx

    mov eax, [esp+4]            ; argument: pointer address

    mov [current_thread], eax   ; update pointer
    mov eax, [eax]              ; the read current_thread object

    mov esp, [eax+0]            ; load
    mov ebp, [eax+4]
    mov ebx, [eax+8]
    mov esi, [eax+12]
    mov edi, [eax+16]

    mov eax, [eax+20]           ; load eflags
    push eax
    popf

    ret                         ; esp: the address of function fn.  Then jmp there