void context_switch(){
pcb * transition;
pcb * temp;
atomic_up();
transition = running;
transition->frame_ptr = old_fp;
if(transition->next_process != NULL){
ready_queue[prio] = ready_queue[prio]->next_process;
temp = ready_queue[prio];
while(temp->next_process != NULL){
temp = temp->next_process;
}
temp->next_process = transition;
transition->next_process = NULL;
}
transition->process_state = READY_STATE;
clear_priority();
while(1){
if(ready_queue[prio] != NULL){
if(ready_queue[prio]->process_state == READY_STATE){
running = ready_queue[prio];
running->process_state = RUNNING_STATE;
old_fp = running->frame_ptr;
atomic_down();
return;
} else if(ready_queue[prio]->process_state == NEW_STATE){
running = ready_queue[prio];
running->process_state = RUNNING_STATE;
atomic_down();
temp_sp = running->stack_ptr;
asm("move.l temp_sp, %d0");
asm("move.l %d0, %a7");
process_bootstrap(running);
return;
}
break;
} else {
prio = (prio + 1) % 4;
}
}
return;
}
/*
* Initial boot sequence.
*/
static
void
boot(void)
{
/*
* The order of these is important!
* Don't go changing it without thinking about the consequences.
*
* Among other things, be aware that console output gets
* buffered up at first and does not actually appear until
* dev_bootstrap() attaches the console device. This can be
* remarkably confusing if a bug occurs at this point. So
* don't put new code before dev_bootstrap if you don't
* absolutely have to.
*
* Also note that the buffer for this is only 1k. If you
* overflow it, the system will crash without printing
* anything at all. You can make it larger though (it's in
* dev/generic/console.c).
*/
kprintf("\n");
kprintf("OS/161 base system version %s\n", BASE_VERSION);
kprintf("%s", harvard_copyright);
kprintf("\n");
kprintf("Andrew K's system version %s (%s #%d)\n",
GROUP_VERSION, buildconfig, buildversion);
kprintf("\n");
ram_bootstrap();
scheduler_bootstrap();
#if OPT_A2
process_bootstrap();
#else // OPT_A2
thread_bootstrap();
#endif
vfs_bootstrap();
dev_bootstrap();
vm_bootstrap();
kprintf_bootstrap();
/* Default bootfs - but ignore failure, in case emu0 doesn't exist */
vfs_setbootfs("emu0");
/*
* Make sure various things aren't screwed up.
*/
assert(sizeof(userptr_t)==sizeof(char *));
assert(sizeof(*(userptr_t)0)==sizeof(char));
/* Assignment 0 Hello World Msg */
#if OPT_A0
hello();
#endif /* OPT_A0 */
#if OPT_A2
kprintf("Process %d initialized.\n", curproc->p_id);
kprintf("Has parent id %d and thread named %s.\n", curproc->p_parent, curproc->p_thread->t_name);
#endif // OPT_A2
}
