void cleanup_execute_tasks(void)
{
while(const cleanup_task_t task = task_pop())
{
task();
}
}
int main()
{
unsigned int stacks[TASK_LIMIT][STACK_SIZE];
//struct task_control_block tasks[TASK_LIMIT];
struct pipe_ringbuffer pipes[PIPE_LIMIT];
struct task_control_block *ready_list[PRIORITY_LIMIT + 1]; /* [0 ... 39] */
struct task_control_block *wait_list = NULL;
//size_t task_count = 0;
size_t current_task = 0;
size_t i;
struct task_control_block *task;
int timeup;
unsigned int tick_count = 0;
SysTick_Config(configCPU_CLOCK_HZ / configTICK_RATE_HZ);
init_rs232();
__enable_irq();
tasks[task_count].stack = (void*)init_task(stacks[task_count], &first);
tasks[task_count].pid = 0;
tasks[task_count].priority = PRIORITY_DEFAULT;
task_count++;
/* Initialize all pipes */
for (i = 0; i < PIPE_LIMIT; i++)
pipes[i].start = pipes[i].end = 0;
/* Initialize fifos */
for (i = 0; i <= PATHSERVER_FD; i++)
_mknod(&pipes[i], S_IFIFO);
/* Initialize ready lists */
for (i = 0; i <= PRIORITY_LIMIT; i++)
ready_list[i] = NULL;
while (1) {
tasks[current_task].stack = activate(tasks[current_task].stack);
tasks[current_task].status = TASK_READY;
timeup = 0;
switch (tasks[current_task].stack->r8) {
case 0x1: /* fork */
if (task_count == TASK_LIMIT) {
/* Cannot create a new task, return error */
tasks[current_task].stack->r0 = -1;
}
else {
/* Compute how much of the stack is used */
size_t used = stacks[current_task] + STACK_SIZE
- (unsigned int*)tasks[current_task].stack;
/* New stack is END - used */
tasks[task_count].stack = (void*)(stacks[task_count] + STACK_SIZE - used);
/* Copy only the used part of the stack */
memcpy(tasks[task_count].stack, tasks[current_task].stack,
used * sizeof(unsigned int));
/* Set PID */
tasks[task_count].pid = task_count;
/* Set priority, inherited from forked task */
tasks[task_count].priority = tasks[current_task].priority;
/* Set return values in each process */
tasks[current_task].stack->r0 = task_count;
tasks[task_count].stack->r0 = 0;
tasks[task_count].prev = NULL;
tasks[task_count].next = NULL;
task_push(&ready_list[tasks[task_count].priority], &tasks[task_count]);
/* There is now one more task */
task_count++;
}
break;
case 0x2: /* getpid */
tasks[current_task].stack->r0 = current_task;
break;
case 0x3: /* write */
_write(&tasks[current_task], tasks, task_count, pipes);
break;
case 0x4: /* read */
_read(&tasks[current_task], tasks, task_count, pipes);
break;
case 0x5: /* interrupt_wait */
/* Enable interrupt */
NVIC_EnableIRQ(tasks[current_task].stack->r0);
/* Block task waiting for interrupt to happen */
tasks[current_task].status = TASK_WAIT_INTR;
break;
case 0x6: /* getpriority */
{
int who = tasks[current_task].stack->r0;
if (who > 0 && who < (int)task_count)
tasks[current_task].stack->r0 = tasks[who].priority;
else if (who == 0)
tasks[current_task].stack->r0 = tasks[current_task].priority;
else
tasks[current_task].stack->r0 = -1;
} break;
case 0x7: /* setpriority */
{
int who = tasks[current_task].stack->r0;
int value = tasks[current_task].stack->r1;
value = (value < 0) ? 0 : ((value > PRIORITY_LIMIT) ? PRIORITY_LIMIT : value);
if (who > 0 && who < (int)task_count)
tasks[who].priority = value;
else if (who == 0)
tasks[current_task].priority = value;
else {
tasks[current_task].stack->r0 = -1;
break;
}
tasks[current_task].stack->r0 = 0;
} break;
case 0x8: /* mknod */
if (tasks[current_task].stack->r0 < PIPE_LIMIT)
tasks[current_task].stack->r0 =
_mknod(&pipes[tasks[current_task].stack->r0],
tasks[current_task].stack->r2);
else
tasks[current_task].stack->r0 = -1;
break;
case 0x9: /* sleep */
if (tasks[current_task].stack->r0 != 0) {
tasks[current_task].stack->r0 += tick_count;
tasks[current_task].status = TASK_WAIT_TIME;
}
break;
default: /* Catch all interrupts */
if ((int)tasks[current_task].stack->r8 < 0) {
unsigned int intr = -tasks[current_task].stack->r8 - 16;
if (intr == SysTick_IRQn) {
/* Never disable timer. We need it for pre-emption */
timeup = 1;
tick_count++;
}
else {
/* Disable interrupt, interrupt_wait re-enables */
NVIC_DisableIRQ(intr);
}
/* Unblock any waiting tasks */
for (i = 0; i < task_count; i++)
if ((tasks[i].status == TASK_WAIT_INTR && tasks[i].stack->r0 == intr) ||
(tasks[i].status == TASK_WAIT_TIME && tasks[i].stack->r0 == tick_count))
tasks[i].status = TASK_READY;
}
}
/* Put waken tasks in ready list */
for (task = wait_list; task != NULL;) {
struct task_control_block *next = task->next;
if (task->status == TASK_READY)
task_push(&ready_list[task->priority], task);
task = next;
}
/* Select next TASK_READY task */
for (i = 0; i < (size_t)tasks[current_task].priority && ready_list[i] == NULL; i++);
if (tasks[current_task].status == TASK_READY) {
if (!timeup && i == (size_t)tasks[current_task].priority)
/* Current task has highest priority and remains execution time */
continue;
else
task_push(&ready_list[tasks[current_task].priority], &tasks[current_task]);
}
else {
task_push(&wait_list, &tasks[current_task]);
}
while (ready_list[i] == NULL)
i++;
current_task = task_pop(&ready_list[i])->pid;
}
return 0;
}
