path: root/src/sys/schedule.c

#include <cpu.h>
#include <globals.h>
#include <graphics/lfb.h>
#include <drivers/uart.h>
#include <lib/kmem.h>
#include <sys/schedule.h>
#include <util/mutex.h>

extern void kernel_usr_task_loop(void);

void init_scheduler(void)
{
	// Set rthread to usrloopthread - an infinitely running thread so that the pointer will never be null
	usrloopthread.pc = (void*)kernel_usr_task_loop;
	usrloopthread.sp = (void*)0x5FC8;
	*(unsigned long**)usrloopthread.sp = (unsigned long*)kernel_usr_task_loop;
	usrloopthread.sp_base = -1;
	usrloopthread.mptr = 0;
	usrloopthread.pid = -1;
	usrloopthread.priority = -1;
	usrloopthread.old_priority = -1;
	usrloopthread.status = THREAD_READY;
	scheduler.rthread = &usrloopthread;
	// Initialize Rotating Buffers
	struct ThreadQueues* tq;
	for (int i = 0; i < PRIORITIES; i++) {
		tq = &scheduler.thread_queues[i];
		struct ThreadRotBuffer* trb = &tq->ready;
		for (int i = 0; i < TQUEUE_CNT; i++) {
			trb->roffset = 0;
			trb->woffset = 0;
			for (int j = 0; j < TQUEUE_MAX; j++)
				trb->queue[j] = 0;
			trb += 1;
		}
	}
	// Initialize nextpid
	nextpid = FIRST_AVAIL_PID;

	for (unsigned long i = 0; i < MAX_THREADS; i++) {
		struct Thread* t = &threads[i];
		t->offset = i;
		t->sp_base = 0x20000000 - STACK_SIZE*i;
	}
}

struct Thread* get_available_thread(void)
{
	for(unsigned long i = 0; i < MAX_THREADS; i++) {
		if (thread_table[i] == 0)
			return &threads[i];
	}
	return 0;
}

void add_thread(void* pc, void* arg, unsigned char priority)
{
	struct Thread* thread = get_available_thread();
	thread_table[thread->offset] = 1;
	thread->pc = pc;
	unsigned long* argp = (void*)thread->sp_base;
	argp -= 13;
	*argp = (unsigned long)arg; // Set r0 to the argument
	argp -= 1;
	*(unsigned long**)argp = (unsigned long*)cleanup; // Set lr to the cleanup function
	thread->sp = argp;
	thread->status = THREAD_READY;
	thread->mptr = (void*)0;
	thread->pid = nextpid++;
	// Reset next pid on overflow
	if (nextpid < FIRST_AVAIL_PID) {
		nextpid = FIRST_AVAIL_PID;
	}
	if (priority >= PRIORITIES)
		thread->priority = PRIORITIES - 1;
	else
		thread->priority = priority;
	thread->old_priority = -1;
	thread->preempt = 0;
	// Add Thread* to scheduler's appropriate buffer
	struct ThreadQueues* tq = &scheduler.thread_queues[thread->priority];
	struct ThreadRotBuffer* trb;
	// Add to stack error queue if stack was not obtained
	trb = &tq->ready;
	trb->queue[trb->woffset++] = thread;
	trb->woffset %= TQUEUE_MAX;
	// Schedule if this was called in usermode
	unsigned long mode = getmode() & 0x1F;
	if (mode == 0x10) {
		sys0(SYS_YIELD_HIGH);
	}
}

void uart_scheduler(void)
{
	uart_string("Scheduler Info\n==============\nCurrent\n");
	uart_hex((unsigned long)scheduler.rthread);
	uart_char(' ');
	kmemshow32((void*)scheduler.rthread, 7);
	struct ThreadQueues* tq;
	for(int p = 0; p < PRIORITIES; p++) {
		uart_string("Priority ");
		uart_10(p);
		uart_char('\n');
		tq = &scheduler.thread_queues[p];
		struct ThreadRotBuffer* trb;
		trb = &tq->ready;
		for(int i = 0; i < TQUEUE_CNT; i++) {
			if (trb->roffset == trb->woffset) {
				trb += 1;
				continue;
			}
			uart_string("Queue ");
			uart_10(i);
			uart_char('\n');
			unsigned long roffset = trb->roffset;
			while (roffset != trb->woffset) {
				uart_hex((unsigned long)trb->queue[roffset]);
				uart_char(' ');
				kmemshow32((void*)trb->queue[roffset], 7);
				roffset++;
				roffset %= TQUEUE_MAX;
			}
			trb += 1;
		}
	}
	uart_string("==============\n");
}

struct Thread* next_thread(void)
{
	struct Thread* next = &usrloopthread;
	// Recurse through all priorities to try to find a ready thread
	for (int p = 0; p < PRIORITIES; p++) {
		struct ThreadRotBuffer* rb = &scheduler.thread_queues[p].ready;
		if (rb->roffset == rb->woffset)
			continue;
		return rb->queue[rb->roffset];
	}
	// No thread found, use basic usrloopthread while waiting for new thread
	return next;
}

void* get_rthread_roffset(void)
{
	return &scheduler.thread_queues[scheduler.rthread->priority].ready.roffset;
}

void yield(void)
{
	struct Thread* rthread = scheduler.rthread;
	// usrloopthread should not be yielded
	if (rthread == &usrloopthread)
		return;
	// Put current thread at the end of its ready queue,
	//  thus any threads of the same priority can be run first
	unsigned char priority = rthread->priority;
	struct ThreadRotBuffer* trb = &scheduler.thread_queues[priority].ready;
	trb->roffset += 1;
	trb->roffset %= TQUEUE_MAX;
	trb->queue[trb->woffset++] = rthread;
	trb->woffset %= TQUEUE_MAX;
}

void sched_mutex_yield(void* m)
{
	struct Thread* rthread = scheduler.rthread;
	// usrloopthread should not be yielded
	if (rthread == &usrloopthread)
		return;
	unsigned char priority = rthread->priority;
	// Signify which lock this thread is waiting for
	rthread->mptr = m;
	struct ThreadRotBuffer* trbb = &scheduler.thread_queues[priority].ready;
	struct ThreadRotBuffer* trbm = &scheduler.thread_queues[priority].mwait;
	// Move to next thread in the current thread priority's ready queue
	trbb->roffset += 1;
	trbb->roffset %= TQUEUE_MAX;
	// Add thread to waiting queue
	trbm->queue[trbm->woffset++] = rthread;
	trbm->woffset %= TQUEUE_MAX;
	// Find the thread with the mutex
	struct ThreadQueues* tq;
	// Search through each priority
	for (int i = 0; i < PRIORITIES; i++) {
		tq = &scheduler.thread_queues[i];
		struct ThreadRotBuffer* trb = &tq->ready;
		// Search through each queue at the current priority
		for (int i = 0; i < TQUEUE_CNT; i++) {
			unsigned long roffset = trb->roffset;
			unsigned long woffset = trb->woffset;
			// Search through the threads
			while(roffset != woffset) {
				// Found thread
				if (trb->queue[roffset]->pid == ((struct Mutex*)m)->pid) {
					// Promote the thread to the new priority
					if (trb->queue[roffset]->priority > priority) {
						trbb->queue[trbb->woffset++] = trb->queue[roffset];
						// Set the old priority if not set
						if(trb->queue[roffset]->old_priority == 0xFF)
							trb->queue[roffset]->old_priority = trb->queue[roffset]->priority;
						// Promote the priority
						trb->queue[roffset]->priority = priority;
						trbb->woffset %= TQUEUE_MAX;
						unsigned long coffset = roffset;
						// Fill gap where the thread was removed
						while (coffset != woffset) {
							trb->queue[coffset] = trb->queue[(coffset+1)%TQUEUE_MAX];
							coffset++;
							coffset %= TQUEUE_MAX;
						}
						// Move the woffset back since the gap was filled in
						if (trb->woffset == 0)
							trb->woffset = TQUEUE_MAX-1;
						else
							trb->woffset--;
					}
					return;
				}
				roffset++;
				roffset %= TQUEUE_MAX;
			}
			// Check next queue in given priority
			trb += 1;
		}
	}
}

void sched_mutex_resurrect(void* m)
{
	// Look through each priority
	for (int p = 0; p < PRIORITIES; p++) {
		struct ThreadRotBuffer* trbm = &scheduler.thread_queues[p].mwait;
		unsigned long roffset = trbm->roffset;
		// Look through the lock wait queue
		while (roffset != trbm->woffset) {
			// Check if the thread is waiting for the released mutex
			if (trbm->queue[roffset]->mptr == m) {
				// Ressurect the thread
				trbm->queue[roffset]->mptr = 0;
				struct ThreadRotBuffer* trb = &scheduler.thread_queues[trbm->queue[roffset]->priority].ready;
				trb->queue[trb->woffset++] = trbm->queue[roffset];
				trb->woffset %= TQUEUE_MAX;
				// Copy all next backward to fill space
				unsigned long coffset = roffset;
				while (coffset != trbm->woffset) {
					trbm->queue[coffset] = trbm->queue[(coffset+1)%TQUEUE_MAX];
					coffset++;
					coffset %= TQUEUE_MAX;
				}
				// Move the woffset back since the space was filled
				if(trbm->woffset == 0)
					trbm->woffset = TQUEUE_MAX-1;
				else
					trbm->woffset--;
				// Move the read pointer ahead
				struct Thread* rthread = scheduler.rthread;
				// Move the current thread to its old priority if it was promoted earlier
				if (rthread->old_priority != 0xFF) {
					struct ThreadRotBuffer* rtrb = &scheduler.thread_queues[rthread->priority].ready;
					struct ThreadRotBuffer* ntrb = &scheduler.thread_queues[rthread->old_priority].ready;
					rtrb->roffset++;
					rtrb->roffset %= TQUEUE_MAX;
					if (ntrb->roffset == 0)
						ntrb->roffset = TQUEUE_MAX-1;
					else
						ntrb->roffset--;
					ntrb->queue[ntrb->roffset] = rthread;
					rthread->priority = rthread->old_priority;
					rthread->old_priority = -1;
				}
				return;
			}
			roffset++;
			roffset %= TQUEUE_MAX;
		}
	}
}

// TODO: Check offsets