bool
in_queue(Direction light_to_push)
{
bool flag = false;
int i = 0;
for (i=q_getstart(next_lights); i!=q_getend(next_lights); i=(i+1)%q_getsize(next_lights)) {
Direction *ptr = q_getguy(next_lights, i);
if (light_to_push == *ptr){
flag = true;
}
}
return flag;
}
/*
* Debugging function to dump the run queue.
*/
void
print_run_queue(void)
{
/* Turn interrupts off so the whole list prints atomically. */
int spl = splhigh();
int i,k=0;
i = q_getstart(runqueue);
while (i!=q_getend(runqueue)) {
struct thread *t = q_getguy(runqueue, i);
kprintf(" %2d: %s %p\n", k, t->t_name, t->t_sleepaddr);
i=(i+1)%q_getsize(runqueue);
k++;
}
splx(spl);
}
void
print_run_queue(void)
{
/* Turn interrupts off so the whole list prints atomically. */
int spl = splhigh();
int i, j, k;
for(i = 0; i < NUM_PRIORITIES; i++)
{
j = q_getstart(runqueue[i]);
k = 0;
kprintf("Priority %d:\n", i);
while (j != q_getend(runqueue[i])) {
struct thread *t = q_getguy(runqueue[i], j);
kprintf(" %2d: %s %p\n", k, t->t_name, t->t_sleepaddr);
j = (j + 1) % q_getsize(runqueue[i]);
k++;
}
}
splx(spl);
}
/*
* Actual scheduler. Returns the next thread to run. Calls cpu_idle()
* if there's nothing ready. (Note: cpu_idle must be called in a loop
* until something's ready - it doesn't know whether the things that
* wake it up are going to make a thread runnable or not.)
*/
struct thread *
scheduler(void)
{
// meant to be called with interrupts off
assert(curspl>0);
while (q_empty(runqueue)) {
cpu_idle();
}
// You can actually uncomment this to see what the scheduler's
// doing - even this deep inside thread code, the console
// still works. However, the amount of text printed is
// prohibitive.
//
//print_run_queue();
/* We will have a defined variable in scheduler.h that will control
the type of scheduling */
if(scheduler_type == SCHEDULER_RANDOM)
{
/* Random queue method */
// We could manipulate q->next_read, an integer that indexes the next in line
// i.e. pick an index based on the size of the queue (q->size), and change
// runqueue->next_read to that index
// We might also be able to just jump in and get a random index from the queue
// queue size is 32 by default
int queue_size = q_getsize(runqueue);
int random_index;
struct thread * temp_thread;
// We will have to get the thread number from within the active part
// of the queue
int start = q_getstart(runqueue);
int end = q_getend(runqueue);
int random_range = (end - start);
// We have a problem if the start and end are the same
assert(random_range != 0);
// The startup code seems to have issues if you pick it right off the bat
if (random_range < 0)
random_range = random_range + queue_size;
// No need to pick a random thread if there is only 1 in the queue
if (random_range == 1)
return q_remhead(runqueue);
DEBUG(DB_THREADS, "Number of active threads: %u.\n", random_range);
DEBUG(DB_THREADS, "Start: %u.\n", start);
DEBUG(DB_THREADS, "End: %u.\n", end);
random_index = (random() % random_range + start) % queue_size;
DEBUG(DB_THREADS, "%u index chosen.\n", random_index);
// Now, we have to move our chosen thread to the front of the line
// There is probably some other way to do this that is more efficient, but
// I had no success with q_getguy()
// We start with the next thread in the queue, and work our way to the chosen one
while(q_getstart(runqueue) != random_index)
{
temp_thread = q_remhead(runqueue);
q_addtail(runqueue, temp_thread);
}
DEBUG(DB_THREADS, "New start: %u.\n", q_getstart(runqueue));
DEBUG(DB_THREADS, "New end: %u.\n", q_getend(runqueue));
return q_remhead(runqueue);
}
else if (scheduler_type == SCHEDULER_MLFQ)
{
/* MLFQ method */
// We will go through all of our queue, looking for the highest priority thread
// By starting at the next read and working up, on a tie we are taking the first in
// queue size is 32 by default
int queue_size = q_getsize(runqueue);
int i;
int chosen_index;
int priority;
int random_choice;
struct thread * temp_thread;
// We will have to get the thread number from within the active part
// of the queue
int start = q_getstart(runqueue);
int end = q_getend(runqueue);
cycles++;
if (cycles > 2000) {
// reset priorities
//kprintf("Resetting priorities");
i = start;
while( i != end)
{
temp_thread = q_getguy(runqueue, i);
DEBUG(DB_THREADS, "Setting priority\n");
thread_set_priority(temp_thread, 50);
i = (i+1) % queue_size;
}
cycles = 0;
// A bit of randomness to prevent immediate restarving
return q_remhead(runqueue);
}
int highest_priority = -1; // 100 is maximum priority
i = start;
while( i != end)
{
temp_thread = q_getguy(runqueue, i);
DEBUG(DB_THREADS, "Getting priority\n");
priority = thread_get_priority(temp_thread);
DEBUG(DB_THREADS, "Priority: %u.\n", priority);
if (priority > highest_priority)
{
chosen_index = i;
highest_priority = priority;
}
// In the event of a tie, random pick
else if (priority == highest_priority)
{
random_choice == random() % 3;
if (random_choice == 0)
chosen_index = i;
}
i = (i+1) % queue_size;
}
DEBUG(DB_THREADS, "Start: %u.\n", start);
DEBUG(DB_THREADS, "End: %u.\n", end);
DEBUG(DB_THREADS, "%u index chosen with priority %u.\n", chosen_index, highest_priority);
//kprintf("%u index chosen with priority %u.\n", chosen_index, highest_priority);
// Now, we have to move our chosen thread to the front of the line
// There is probably some other way to do this that is more efficient, but
// I had no success with q_getguy()
// We start with the next thread in the queue, and work our way to the chosen one
while(q_getstart(runqueue) != chosen_index)
{
temp_thread = q_remhead(runqueue);
q_addtail(runqueue, temp_thread);
}
DEBUG(DB_THREADS, "New start: %u.\n", q_getstart(runqueue));
DEBUG(DB_THREADS, "New end: %u.\n", q_getend(runqueue));
return q_remhead(runqueue);
}
// Fall through to default FIFO scheduler
return q_remhead(runqueue);
}
void enter_kitchen(const int creature_type) {
/*
* Policy: Let any amount of cats try to access any amount of bowls at once,
* or let any amount of mice try to access any amount of bowls at once, but
* never mix.
*
* So, if the kitchen is empty, the first creature can enter regardless. If
* that creature is a mouse, let all subsequent creatures that are mice enter
* without delay. But, as soon as the next creature is a cat, stop letting
* all subsequent creatures in, and put them in groups waiting in line.
* Idea is to wait until all the mice currently in the kitchen are done, then
* let a "burst" of cats in, then wait until all of them are done, then let a
* "burst" of mice in, etc.
*
* For example, if x's are mice, and y's are cats, say we have this stream of
* animals (arrived at the kitchen in order from right to left)
*
* Time | Outside of Kitchen | Inside Kitchen | Done eating
* t0 yyyxyyyyyxxxxxxyyyyxx
* t1 yyyxyyyyyxxxxxxyyyy xx
* t2 yyyxyyyyyxxxxxx yyyy xx
* t3 yyyxyyyyy xxxxxx yyyyxx
*
*
* This policy has the objective of being as fair as possible, with efficieny
* as an important but secondary objective (we let any amount of 1 creature
* type in at once). Besides, we are multithreading to get a huge efficiency
* gain in the first place.
*/
// Want mutual exclusion for group processing
lock_acquire(k->kitchen_lock);
// First creature in gets to initially set the current_creature flag and enter
if (k->current_creature == 2) {
k->current_creature = creature_type;
}
/*
* If the queue is not empty, know that there are other groups to go first.
* Don't barge ahead of another group even if you match the current creature.
*/
else if (!q_empty(k->group_list)) {
// Inspect the last group in line
int index = q_getend(k->group_list) > 0 ? q_getend(k->group_list)-1 : q_getsize(k->group_list) - 1;
struct kgroup *g = (struct kgroup *)q_getguy(k->group_list, index);
if (g->type == creature_type) {
// If the last group is of your type, merge into that group
g->amount++;
} else {
// Otherwise, start a new last group
g = kmalloc(sizeof(struct kgroup));
g->type = creature_type;
g->amount = 1;
// Enqueue new group
q_addtail(k->group_list, g);
}
// Wait
cv_wait(k->kitchen_cv, k->kitchen_lock);
}
/*
* If we aren't the first creature, and the queue is empty, check if we match the
* creature currently in the kitchen. If not, we are going to start the only group
* in the queue.
*/
else if (k->current_creature != creature_type) {
// Create a group struct
struct kgroup *g = kmalloc(sizeof(struct kgroup));
// Group is of your type with 1 creature so far
g->type = creature_type;
g->amount = 1;
// Enqueue new group
q_addtail(k->group_list, g);
// Wait
cv_wait(k->kitchen_cv, k->kitchen_lock);
}
// If here, we have been granted access to the kitchen
// Set the creature type currently owning the kitchen
k->current_creature = creature_type;
// Increment creature count
k->creature_count++;
/*
* Release kitchen lock before accessing the bowls, because we want any amount
* of one type of creature to be able to access the bowls at once.
*/
lock_release(k->kitchen_lock);
}
