Scheduler Rewrite Start

6 files changed, 415 insertions, 308 deletions

diff --git a/later/schedule.S b/later/schedule.S
index 1811c7c..a46654c 100644
--- a/later/schedule.S
+++ b/later/schedule.S
@@ -1,58 +1,143 @@
-.section .text
-.globl preserveregs
-preserveregs:
-	str r4,  [r0, #0x10]
-	str r5,  [r0, #0x14]
-	str r6,  [r0, #0x18]
-	str r7,  [r0, #0x1c]
-	str r8,  [r0, #0x20]
-	str r9,  [r0, #0x24]
-	str r10, [r0, #0x28]
-	str r11, [r0, #0x2c]
-	bx lr
-
-.globl restoreregs
-restoreregs:
-	ldr r4,  [r0, #0x10]
-	ldr r5,  [r0, #0x14]
-	ldr r6,  [r0, #0x18]
-	ldr r7,  [r0, #0x1c]
-	ldr r8,  [r0, #0x20]
-	ldr r9,  [r0, #0x24]
-	ldr r10, [r0, #0x28]
-	ldr r11, [r0, #0x2c]
-	bx lr
+.section ".text"
+.globl schedule
+// TODO: Implement Scheduler for IRQ
 
-.globl exetask
-exetask:
-	push {r0, r4, r5, r6, r7, r8, r9, r10, r11, lr}
-	// Restore registers from context switch
-	ldr r4,  [r0, #0x10]
-	ldr r5,  [r0, #0x14]
-	ldr r6,  [r0, #0x18]
-	ldr r7,  [r0, #0x1c]
-	ldr r8,  [r0, #0x20]
-	ldr r9,  [r0, #0x24]
-	ldr r10, [r0, #0x28]
-	ldr r11, [r0, #0x2c]
 
-	// Preserve system stack
-	ldr r1,  =msp
-	str sp, [r1]
-	// Setup task's stack
-	ldr sp, [r0, #0x34]
-	// Switch to task
-	ldr lr, [r0, #0x3c]
-	blx lr
-	// Restore system stack
-	ldr r1, =msp
-	ldr sp, [r1]
-	pop {r0, r4, r5, r6, r7, r8, r9, r10, r11, pc}
+// Save Context
+// reg = struct cpu_context*
+.macro save_context reg
+	str r4,  [\reg, #0x00]
+	str r5,  [\reg, #0x04]
+	str r6,  [\reg, #0x08]
+	str r7,  [\reg, #0x0c]
+	str r8,  [\reg, #0x10]
+	str r9,  [\reg, #0x14]
+	str r10, [\reg, #0x18]
+	str r11, [\reg, #0x1c]
+	str r12, [\reg, #0x20]
+	str lr,  [\reg, #0x24]
+.endm
+// Restore Context
+// reg = struct cpu_context*
+.macro restore_context reg
+	ldr r4, [\reg, #0x00]
+	ldr r5, [\reg, #0x04]
+	ldr r6, [\reg, #0x08]
+	ldr r7, [\reg, #0x0c]
+	ldr r8, [\reg, #0x10]
+	ldr r9, [\reg, #0x14]
+	ldr r10, [\reg, #0x18]
+	ldr r11, [\reg, #0x1c]
+	ldr r12, [\reg, #0x20]
+	ldr lr , [\reg, #0x24]
+.endm
 
-.section .data
-msp:
-	.space 4
-.section .data.stacks
-.globl stacks
-stacks:
-	.space 0x100000
+// Implemented the scheduler in Assembly since the C defined was messing around with the program stacks
+//  This way, I can be confident that the stacks will be unchanged
+schedule:
+	ldr r3, =scheduler
+	// Preserve context
+	ldr r0, [r3, #4]
+	// r0 = struct cpu_context*
+	save_context r0
+	// Get the next available thread
+	push {r1-r3, lr}
+	bl get_next_thread
+	pop {r1-r3, lr}
+	ldr r1,  [r3, #0] 
+	// r3 = struct Scheduler*
+	// r0 = struct LL* next_thread_ll
+	// r1 = struct LL* current_thread_ll
+	// Check if there is a valid currently running thread
+	cmp r1, #0
+	beq schedule.current_thread_nexists
+schedule.current_thread_exists:
+	cmp r0, r1
+	beq schedule.run_current
+	cmp r0, #0
+	moveq r0, r1 // Make the current running thread the next running thread if no next running thread
+	// Next is not the same as the current
+	// Preserve stack of current
+	ldr r2,  [r1, #0x8] // struct Thread* current
+	ldrh r1, [r2, #0x0e]
+	cmp r1, #2 // THREAD_WAITING
+	beq schedule.temp_status
+	cmp r1, #1 // THREAD_RUNNING
+	bne schedule.dont_modify_status
+schedule.temp_status:
+	mov r1, #0 // THREAD_READY
+	strh r1, [r2, #0x0e]
+schedule.dont_modify_status:
+	str sp,  [r2, #0x4] // void* stack // Preserve stack
+	// Preserve program counter of current
+	str lr,  [r2, #0x0] // void* thread // Preserve pc
+	ldr r2,  [r0, #0x8] // struct Thread* next
+	// Set new stack pointer
+	ldr sp,  [r2, #0x4]
+	// Set the thread as running
+	mov r1, #1 // THREAD_RUNNING
+	strh r1,  [r2, #0x0e] // unsigned short status
+	add r2,  r2, #0x18
+	// Set new running thread
+	str r0,  [r3, #0x0] // struct LL* next_thread_ll // Set new running thread
+	// Set new context
+	str r2,  [r3, #0x4] // struct cpu_context* ctx // Set new context
+	b schedule.run_current
+schedule.current_thread_nexists:
+	// r0 = struct LL* next_thread_ll
+	// r1 = 0 = struct LL* current_thread_ll
+	cmp r0, #0
+	beq schedule.no_next_thread
+	ldr r1, [r0, #0x8]
+	// r1 =  struct Thread* next_thread
+	// Store system stack pointer
+	ldr r2, =svcsp
+	push {r1}
+	ldr r1, [r2]
+	cmp r1, #0
+	pop {r1}
+	bne schedule.dont_overwrite_sys_stack
+	// Store if zero system stack
+	str sp, [r2]
+schedule.dont_overwrite_sys_stack:
+	// Move stack to next thread's stack pointer
+	ldr sp, [r1, #0x4] // void* stack
+	// Store the running thread ll entry
+	str r0, [r3, #0x0] // struct LL* rthread_ll
+	ldr r2, [r0, #0x8] // struct Thread* thread
+	mov r0, #1 // THREAD_RUNNING
+	strh r0, [r2, #0x0e]
+	// Set context
+	add r1, r1, #0x18 // struct cpu_context*
+	str r1, [r3, #0x4] // store to scheduler.ctx
+schedule.run_current:
+	// Restore context
+	ldr r2,  [r3, #0x4] // struct cpu_context* ctx // Set new context
+	restore_context r2
+	// Run
+	ldr r1, [r3, #0]
+	// r1 = struct LL* rthread_ll
+	ldr r1, [r1, #0x8]
+	// r1 = struct Thread* rthread
+	ldr r0, [r1, #0x0]
+	// r0 = void* thread
+	bx r0
+schedule.no_next_thread:
+	// r0 = 0 = struct LL* next_thread_ll
+	// r1 = 0 = struct LL* current_thread_ll
+	// No thread to run
+	// Restore sys context
+	ldr r0, =svccpu
+	str r0, [r3, #0x4] // Store context
+	ldr r0, =svcsp
+	ldr r1, [r0]
+	cmp r1, #0
+	beq schedule.exit
+	mov sp, r1 // Restore stack pointer
+	mov r1, #0
+	str r1, [r0] // Clear stack pointer
+schedule.exit:
+	// Restore register context
+	ldr r2,  [r3, #0x4] // struct cpu_context* ctx // Set new context
+	restore_context r2
+	bx lr
diff --git a/later/schedule.c b/later/schedule.c
index 8cf2780..c300ae0 100644
--- a/later/schedule.c
+++ b/later/schedule.c
@@ -1,83 +1,167 @@
-#include "../sys/schedule.h"
-#include "../lib/ll.h"
-#include "../lib/q.h"
+#include <cpu/irq.h>
+#include <drivers/uart.h>
+#include <globals.h>
+#include <sys/core.h>
+#include <sys/schedule.h>
+#include <util/mutex.h>
 
-#ifdef IGNORE
-#ifdef FLAT
-static struct Task* task_list[256];
-
-static struct Scheduler scheduler = {
-	.tasks = task_list,
-};
-
-static unsigned int ntask_i = 0;
-
-void add_task(struct Task* t)
+void init_scheduler(void)
 {
-	scheduler.tasks[ntask_i] = t;
-	ntask_i += 1;
-	if (ntask_i > 256) {
-		ntask_i = 0;
+	for(int i = 0; i < PRIORITIES; i++) {
+		scheduler.tlist[i].prev = &scheduler.tlist[i];
+		scheduler.tlist[i].next = &scheduler.tlist[i];
+		scheduler.tlist[i].data = 0;
 	}
+	scheduler.rthread_ll = 0;
+	scheduler.ctx = &svccpu;
 }
 
-unsigned int get_task_length(void)
+void* get_stack(void)
 {
-	return ntask_i;
+	for (int i = 0; i < MAX_THREADS; i++) {
+		if (stacks_table[i] == 0) {
+			stacks_table[i] = 1;
+			return (void*)heap_end() - STACK_SIZE*i;
+		}
+	}
+	return 0;
 }
 
-void execute_task(void)
+void add_thread(void (*thread_fxn)(void), unsigned char priority)
 {
-	if (scheduler.tasks[ntask_i-1] != 0)
-		scheduler.tasks[ntask_i-1]->task();
+	struct Thread* thread = (struct Thread*)malloca(sizeof(struct Thread), 4);
+	// Set the program counter to the entry
+	thread->thread = thread_fxn;
+	// Get a stack frame
+	thread->stack_base = get_stack();
+	thread->stack = thread->stack_base;
+	// Put in error state for no stack
+	if(thread->stack == 0)
+		thread->data.status = THREAD_STACK_ERROR;
+	else
+		thread->data.status = THREAD_READY;
+	// Doesn't wait for mutex at start
+	thread->data.mutex_waiting = 0;
+	// Set PID
+	thread->data.pid = nextpid++;
+	thread->data.preempt_count = 0;
+	thread->data.cpu_context.lr = (unsigned long)cleanup;
+	unsigned char p = priority;
+	if (p >= PRIORITIES) {
+		p = PRIORITIES - 1;
+	}
+	thread->data.priority = p;
+	push_ll(&scheduler.tlist[p], thread);
 }
-#elseif LL
-static struct LL bl = {
-	.prev = 0,
-	.next = 0,
-};
-static struct Scheduler scheduler = {
-	.tasks = &bl,
-};
-#else
-static struct Q_base bq = {
-	.next = 0,
-	.last = 0,
-};
-static struct Scheduler  scheduler = {
-	.tasks = &bq,
-};
 
-void add_task(struct Task* t)
+struct LL* get_next_thread(void)
 {
-	pushq(scheduler.tasks, t);
+	for(unsigned long i = 0; i < PRIORITIES; i++) {
+		struct LL* thread_ll = scheduler.tlist[i].next;
+		if (thread_ll == &scheduler.tlist[i])
+			continue;
+		do {
+			struct Thread* thread = thread_ll->data;
+			if((thread->data.status == THREAD_RUNNING) || (thread->data.status == THREAD_READY))
+				return thread_ll;
+			thread_ll = thread_ll->next;
+		} while(thread_ll != &scheduler.tlist[i]);
+	}
+	return 0;
 }
 
-unsigned int get_task_length(void)
+void schedule_c(void)
 {
-	unsigned int length = 0;
-	if (scheduler.tasks->last == 0)
-		return length;
-	else if (scheduler.tasks->next == scheduler.tasks->last)
-		return 1;
-	else {
-		struct Q* q = scheduler.tasks->next;
-		length += 1;
-		while (q->next != 0) {
-			q = q->next;
-			length += 1;
+	// Preserve registers in current context
+	preserve_ctx(scheduler.ctx);
+
+	// Get current thread
+	struct LL* current_thread_ll = scheduler.rthread_ll;
+	// Get next thread
+	struct LL* next_thread_ll = get_next_thread();
+
+	// If there is a current thread
+	if (current_thread_ll != 0) {
+		// If we are switching the thread
+		if (current_thread_ll != next_thread_ll) {
+			// Context switch
+			struct Thread* current_thread = current_thread_ll->data;
+			struct Thread* next_thread = next_thread_ll->data;
+			preserve_stack(current_thread);
+			//preserve_pc(current_thread);
+			current_thread->thread = (void*)current_thread->data.cpu_context.lr;
+			restore_stack(next_thread);
+			scheduler.rthread_ll = next_thread_ll;
+			scheduler.ctx = &next_thread->data.cpu_context;
 		}
-		return length;
 	}
+	else if (next_thread_ll != 0) {
+		struct Thread* next_thread = next_thread_ll->data;
+		preserve_sys_stack(&svcsp);
+		restore_stack(next_thread);
+		scheduler.rthread_ll = next_thread_ll;
+		scheduler.ctx = &next_thread->data.cpu_context;
+	}
+	if (scheduler.rthread_ll) {
+		struct Thread* rthread = scheduler.rthread_ll->data;
+		restore_ctx(scheduler.ctx);
+		asm volatile ("bx %0" :: "r"(rthread->thread));
+	} else {
+		scheduler.ctx = &svccpu;
+		restore_sys_stack(&svcsp);
+		restore_ctx(scheduler.ctx);
+	}
+}
+
+void cleanup(void)
+{
+	if (scheduler.rthread_ll != 0) {
+		// Mark the thread as finished
+		struct Thread* t = scheduler.rthread_ll->data;
+		//uart_string("Cleaning up thread ");
+		//uart_10(t->data.pid);
+		//uart_char('\n');
+		t->data.status = THREAD_FINISHED;
+		// Mark the stack space as free
+		unsigned long sidx = (unsigned long)(heap_end() - t->stack_base)/STACK_SIZE;
+		stacks_table[sidx] = 0;
+		// Remove the thread
+		struct LL* ll = scheduler.rthread_ll;
+		struct LL* prev = ll->prev;
+		struct LL* next = ll->next;
+		prev->next = ll->next;
+		next->prev = ll->prev;
+		free(ll->data);
+		free(ll);
+		scheduler.rthread_ll = 0;
+	}
+	// Schedule next thread
+	schedule();
 }
 
-void execute_task(void)
+void sched_info(void)
 {
-	if (scheduler.tasks->last != 0) {
-		struct Task* tsk = (struct Task*)scheduler.tasks->next->data;
-		(tsk->task)();
-		popq(scheduler.tasks);
+	uart_string("Scheduler Information\n");
+	for(unsigned long i = 0; i < PRIORITIES; i++) {
+		struct LL* ll = scheduler.tlist[i].next;
+		uart_string("Queue ");
+		uart_10(i);
+		while (ll != &scheduler.tlist[i]) {
+			uart_string("\nThread ");
+			struct Thread* t = ll->data;
+			uart_hex((unsigned long)t->thread);uart_char(' ');
+			uart_hex((unsigned long)t->stack);uart_char(' ');
+			uart_hex((unsigned long)t->stack_base);uart_char(' ');
+			uart_10(t->data.priority);uart_char(' ');
+			uart_10(t->data.preempt_count);uart_char(' ');
+			uart_10(t->data.status);uart_char(' ');
+			uart_hex((unsigned long)t->data.mutex_waiting);uart_char(' ');
+			uart_10(t->data.pid);uart_char('\n');
+			memshow32((unsigned long*)&t->data.cpu_context, 10);
+			ll = ll->next;
+		}
+		uart_char('\n');
 	}
+	uart_string("Stacks:\n");
+	memshow32((unsigned long*)stacks_table, 6);
 }
-#endif
-#endif
diff --git a/later/schedule.flat.c b/later/schedule.flat.c
deleted file mode 100644
index 6eb0d14..0000000
--- a/later/schedule.flat.c
+++ /dev/null
@@ -1,32 +0,0 @@
-#ifdef FLAT
-
-#include "../sys/schedule.h"
-static struct Task* task_list[256];
-
-static struct Scheduler scheduler = {
-	.tasks = task_list,
-};
-
-static unsigned int ntask_i = 0;
-
-void add_task(struct Task* t)
-{
-	scheduler.tasks[ntask_i] = t;
-	ntask_i += 1;
-	if (ntask_i > 256) {
-		ntask_i = 0;
-	}
-}
-
-unsigned int get_task_length(void)
-{
-	return ntask_i;
-}
-
-void execute_task(void)
-{
-	if (scheduler.tasks[ntask_i-1] != 0)
-		scheduler.tasks[ntask_i-1]->task();
-}
-
-#endif
diff --git a/later/schedule.h b/later/schedule.h
index 77da7eb..e1cde57 100644
--- a/later/schedule.h
+++ b/later/schedule.h
@@ -1,43 +1,144 @@
 #ifndef SYS_SCHEDULE_H
 #define SYS_SCHEDULE_H
+#include <cpu.h>
+#include <lib/mem.h>
+#include <lib/ll.h>
+#include <sys/core.h>
 
-#define S_WAITING 0
-#define S_READY 1
+enum ThreadStatus {
+	THREAD_READY = 0,
+	THREAD_RUNNING = 1,
+	THREAD_WAITING = 2,
+	THREAD_WAITING_FOR_MUTEX = 3,
+	THREAD_FINISHED = 4,
+	THREAD_STACK_ERROR = 5,
+};
+
+struct cpu_context {
+	unsigned long r4;
+	unsigned long r5;
+	unsigned long r6;
+	unsigned long r7;
+	unsigned long r8;
+	unsigned long r9;
+	unsigned long r10;
+	unsigned long r11;
+	unsigned long r12;
+	unsigned long lr;
+};
 
-#define STACK_SIZE 0x800
-struct Task {
+struct ThreadData {
 	unsigned char priority;
-	unsigned char status;
+	unsigned char preempt_count;
+	unsigned short status;
+	void* mutex_waiting;
 	unsigned long pid;
-	void (*task)(void);
-	unsigned long reg[16];
-	unsigned long stacki;
-	void* stack;
+	struct cpu_context cpu_context;
 };
 
-#ifdef FLAT
-struct Scheduler {
-	unsigned long running_pid;
-	struct Task** tasks;
-};
-#elseif LL
-#include "../lib/ll.h"
-struct Scheduler {
-	unsigned long running_pid;
-	struct LL* tasks;
+struct Thread {
+	//void (*thread)(void);
+	void* thread;
+	void* stack;
+	void* stack_base;
+	struct ThreadData data;
 };
-#else
-#include "../lib/q.h"
+
+#define MAX_THREADS 0x100
+#define STACK_SIZE 0x1000
+#define PRIORITIES 6
 struct Scheduler {
-	unsigned long running_pid;
-	struct Q_base* tasks;
+	struct LL* rthread_ll;
+	struct cpu_context* ctx;
+	struct LL tlist[PRIORITIES];
 };
-#endif
 
-void add_fxn(void (*task)(void), unsigned char priority);
-unsigned char exists(void (*task)(void));
-void add_no_repeat(void (*task)(void), unsigned char priority);
-unsigned int get_task_length(void);
-void execute_task(void);
+void init_scheduler(void);
+void add_thread(void (*thread_fxn)(void), unsigned char priority);
+extern void schedule(void);
+void schedule_c(void);
+void schedule_irq(void);
+void cleanup(void);
+void sched_info(void);
+struct LL* get_next_thread(void);
+
+static inline void preserve_stack(struct Thread* thread)
+{
+	// Get current mode
+	unsigned long mode = getmode();
+	// Set supervisor mode - "User mode"
+	setsvc();
+	// Store the stack pointer
+	void* ssp = getsp() + 4*4; // Ignore 4 words pushed on by (schedule)
+	thread->stack = ssp;
+	// Restore mode
+	setmode(mode);
+}
+
+static inline void restore_stack(struct Thread* thread)
+{
+	// Get current mode
+	unsigned long mode = getmode();
+	// Set supervisor mode - "User mode"
+	setsvc();
+	// Set stack pointer to thread's stack pointer
+	asm volatile("mov sp, %0" :: "r"(thread->stack));
+	// Restore mode
+	setmode(mode);
+}
+
+static inline void preserve_sys_stack(unsigned long* sp)
+{
+	if (*sp == 0) {
+		unsigned long mode = getmode();
+		setsvc();
+		*sp = (unsigned long)getsp();
+		setmode(mode);
+	}
+}
+
+static inline void restore_sys_stack(unsigned long* sp)
+{
+	if (*sp) {
+		unsigned long mode = getmode();
+		setsvc();
+		setsp((void*)*sp);
+		setmode(mode);
+		*sp = 0;
+	}
+}
+
+static inline void preserve_pc(struct Thread* t)
+{
+	t->thread = (void*)t->data.cpu_context.lr;
+}
+
+static inline void preserve_ctx(struct cpu_context* cpuctx)
+{
+	asm volatile ("mov %0, r4" : "=r"(cpuctx->r4));
+	asm volatile ("mov %0, r5" : "=r"(cpuctx->r5));
+	asm volatile ("mov %0, r6" : "=r"(cpuctx->r6));
+	asm volatile ("mov %0, r7" : "=r"(cpuctx->r7));
+	asm volatile ("mov %0, r8" : "=r"(cpuctx->r8));
+	asm volatile ("mov %0, r9" : "=r"(cpuctx->r9));
+	asm volatile ("mov %0, r10" : "=r"(cpuctx->r10));
+	asm volatile ("mov %0, r11" : "=r"(cpuctx->r11));
+	asm volatile ("mov %0, r12" : "=r"(cpuctx->r12));
+	asm volatile ("mov %0, lr" : "=r"(cpuctx->lr));
+}
+
+static inline void restore_ctx(struct cpu_context* cpuctx)
+{
+	asm volatile ("mov r4,  %0" :: "r"(cpuctx->r4));
+	asm volatile ("mov r5,  %0" :: "r"(cpuctx->r5));
+	asm volatile ("mov r6,  %0" :: "r"(cpuctx->r6));
+	asm volatile ("mov r7,  %0" :: "r"(cpuctx->r7));
+	asm volatile ("mov r8,  %0" :: "r"(cpuctx->r8));
+	asm volatile ("mov r9,  %0" :: "r"(cpuctx->r9));
+	asm volatile ("mov r10, %0" :: "r"(cpuctx->r10));
+	asm volatile ("mov r11, %0" :: "r"(cpuctx->r11));
+	asm volatile ("mov r12, %0" :: "r"(cpuctx->r12));
+	asm volatile ("mov lr,  %0" :: "r"(cpuctx->lr));
+}
 
 #endif
diff --git a/later/schedule.ll.c b/later/schedule.ll.c
deleted file mode 100644
index d9ab954..0000000
--- a/later/schedule.ll.c
+++ /dev/null
@@ -1,13 +0,0 @@
-#ifdef LL
-
-#include "../sys/schedule.h"
-#include "../lib/ll.h"
-static struct LL bl = {
-	.prev = 0,
-	.next = 0,
-};
-static struct Scheduler scheduler = {
-	.tasks = &bl,
-};
-
-#endif
diff --git a/later/schedule.q.c b/later/schedule.q.c
deleted file mode 100644
index 4a5ff85..0000000
--- a/later/schedule.q.c
+++ /dev/null
@@ -1,118 +0,0 @@
-#if !(defined(LL) || defined(FLAT))
-#include "../sys/schedule.h"
-#include "../lib/q.h"
-#include "../lib/mem.h"
-#include "../drivers/uart.h"
-
-extern void preserveregs(void*);
-extern void restoreregs(void*);
-extern void exetask(void*);
-
-static unsigned long next_pid = 3;
-unsigned char table[256] = {0, };
-
-static struct __attribute__((packed,align(4))) Q_base bq = {
-	.next = 0,
-	.last = 0,
-};
-struct __attribute__((packed,align(4))) Scheduler scheduler = {
-	.running_pid = 0,
-	.tasks = &bq,
-};
-
-extern unsigned long __stacks_start;
-
-unsigned long getstack(void)
-{
-	for(unsigned int i = 0; i < 256; i++) {
-		if (table[i] == 0) {
-			table[i] = 1;
-			return i;
-		}
-	}
-	return -1;
-}
-
-void add_fxn(void (*task)(void), unsigned char priority)
-{
-	struct Task* t = (struct Task*)malloc(sizeof(struct Task));
-	// Allocate a stack frame and space for registers to be preserved on context switches
-	t->priority = priority;
-	t->task = task;
-	t->stacki = getstack();
-	t->pid = next_pid;
-	next_pid += 1;
-	if(t->stacki > 256)
-		t->stack = 0;
-	else
-		t->stack = (void*)(__stacks_start + STACK_SIZE*t->stacki);
-	t->status = S_READY;
-	for(unsigned char i = 0; i < 13; i++)
-		t->reg[i] = 0;
-	t->reg[13] = (unsigned long)t->stack;
-	t->reg[14] = 0; // LR
-	t->reg[15] = (unsigned long)task; // PC
-	pushq(scheduler.tasks, t);
-}
-
-unsigned char exists(void (*task)(void))
-{
-	if (scheduler.tasks->next == 0)
-		return 0;
-	struct Q* q = scheduler.tasks->next;
-	while (q != 0) {
-		struct Task* t = q->data;
-		if (t->task == task)
-			return 1;
-		q = q->next;
-	}
-	return 0;
-}
-
-void add_no_repeat(void (*task)(void), unsigned char priority)
-{
-	if (!(exists(task)))
-		add_fxn(task, priority);
-}
-
-unsigned int get_task_length(void)
-{
-	unsigned int length = 0;
-	if (scheduler.tasks->last == 0)
-		return length;
-	else if (scheduler.tasks->next == scheduler.tasks->last)
-		return 1;
-	else {
-		struct Q* q = scheduler.tasks->next;
-		length += 1;
-		while (q->next != 0) {
-			q = q->next;
-			length += 1;
-		}
-		return length;
-	}
-}
-void execute_task(void)
-{
-	// Preserve Current Running PID's Data
-	if (scheduler.tasks->last != 0) {
-		struct Q* q = (struct Q*)scheduler.tasks->next;
-		while (((struct Task*)q->data)->status == S_WAITING) {
-			q = q->next;
-		}
-		struct Task* tsk = (struct Task*)q->data;
-		// Restore registers 
-		//  Including program counter as the entry point
-		//  Including allocated stack position
-		//  Set lr to the return address to restore system stack
-		//preserveregs(tsk->reg);
-		//restoreregs(tsk->reg);
-		scheduler.running_pid = tsk->pid;
-		exetask(tsk->reg);
-		scheduler.running_pid = 0;
-		table[tsk->stacki] = 0;
-		popq(scheduler.tasks);
-	}
-}
-
-#endif