scheduler.c

#include "scheduler.h"
#include "screen.h"

void scheduler_init() {
    next_sch_pid = 0;     
    curr_sch_pid = 0;
}

process_t *get_next_process() {
    process_t *next_process = processes[next_sch_pid];

    curr_sch_pid = next_sch_pid;

    next_sch_pid++;
	next_sch_pid = next_sch_pid % process_count;

    return next_process;
}

void scheduler(int eip, int edi, int esi, int ebp, int esp, int ebx, 
        int edx, int ecx, int eax) {

    process_t *curr_process;

    print("EAX = ");
    printi(eax);
    println();
    
    curr_process = processes[curr_sch_pid];
    next_process = get_next_process();
    
    // saving the current process state
    if (curr_process->state == RUNNING) {
        curr_process->context.eax = eax;
        curr_process->context.ebx = ebx;
        curr_process->context.ecx = ecx;
        curr_process->context.edx = edx;
        curr_process->context.esp = esp;
        curr_process->context.ebp = ebp;
        curr_process->context.esi = esi;
        curr_process->context.edi = edi;
        curr_process->context.eip = eip;
    }

    curr_process->state = READY;
    
    // next lines of code use inline assembly to load the next process
    asm( "	mov %0, %%eax;	\
			mov %0, %%ecx;	\
			mov %0, %%edx;	\
			mov %0, %%ebx;	\
			mov %0, %%esi;	\
			mov %0, %%edi;" 
			: : "r" ( next_process->context.eax ), 
                "r" ( next_process->context.ecx ), 
                "r" ( next_process->context.edx ), 
                "r" ( next_process->context.ebx ),
				"r" ( next_process->context.esi ), 
                "r" ( next_process->context.edi )
    );

    next_process->state = RUNNING;
}

void run_next_process() {
    asm("sti; \ 
         jmp *%0" : : "r" (next_process->context.eip) );
}