/*
* uthread_switch()
*
* This is where all the magic is. Wait until there is a runnable thread, and
* then switch to it using uthread_swapcontext(). Make sure you pick the
* highest priority runnable thread to switch to. Also don't forget to take
* care of setting the ON_CPU thread state and the current thread. Note that
* it is okay to switch back to the calling thread if it is the highest
* priority runnable thread.
*
* Every time uthread_switch() is called, uthread_idle() should be called at
* least once. In addition, when there are no runnable threads, you should
* repeatedly call uthread_idle() until there are runnable threads. Threads
* with numerically higher priorities run first. For example, a thread with
* priority 8 will run before one with priority 3.
* */
void
uthread_switch(void)
{
//we change the location of
//the first thread: it might be put in runnable queue
//or it might be just switched
uthread_t * old_thr = ut_curthr;
//check the state
if( old_thr -> ut_state == UT_RUNNABLE){
//called by uthread_yield
uthread_add_to_runnable_queue(old_thr);
}
else{
//wont add to the runnable queue
}
uthread_idle();
while(1){
//get the next runnable thread.
//from highest priority queue to low priority queue
int i = UTH_MAXPRIO;
/*
for(; i >= 0; i --){
printf("%d:%d\n", i, runq_table[i].tq_size);
}
i = UTH_MAXPRIO;
*/
uthread_t* next_thread = NULL;
for(; i >= 0; i --){
if( !utqueue_empty(&runq_table[i])){
//printf("%d:%d\n", i, runq_table[i].tq_size);
next_thread = utqueue_dequeue(&runq_table[i]);
break;
}
}
if(next_thread != NULL){
//switch!
next_thread->ut_state = UT_ON_CPU;
ut_curthr = next_thread;
uthread_swapcontext(& old_thr -> ut_ctx, &ut_curthr -> ut_ctx);
return;
}
//no runnable threads
//TODO: Rewrtie uthread_idle
else{
uthread_idle();
}
}
}
/*
* uthread_switch()
*
* Wait until there is a runnable thread, and then switch to it using
* uthread_swapcontext().
*
*/
void
uthread_switch(void)
{
int i = 0;
while (1)
{
uthread_idle();
for(i = UTH_MAXPRIO; i >= 0; i--)
{
if (!utqueue_empty(&runq_table[i]))
{
uthread_t* backup = ut_curthr;
uthread_t* new_thread = utqueue_dequeue(&runq_table[i]);
assert(new_thread->ut_state == UT_RUNNABLE);
assert(new_thread->ut_link.l_prev == NULL &&
new_thread->ut_link.l_next == NULL);
/* Swap the new thread */
ut_curthr = new_thread;
ut_curthr->ut_state = UT_ON_CPU;
/* Swap context */
uthread_swapcontext(&backup->ut_ctx, &ut_curthr->ut_ctx);
return;
}
}
}
}
