在aCoral操作系统中,线程退出采用了和Linux一样的方式,线程函数不用死等或显示调用退出相关函数,也就是说用户不用担心函数执行完后的事情。
uc/OS II任务函数与退出
void test(void *ptr){
Do_something();
while(1);
}
void test(void *ptr){
Do_something();
EXIT();
}
void acoral_thread_exit(){
acoral_kill_thread(acoral_cur_thread);
}
typedef struct{
acoral_res_t res; //event也是一种资源
unsigned char type; //ACORAL_EVENT_SEM或ACORAL_EVENT_MUTEX
int count; //
acoral_list_t wait_queue;
char *name;
void *data;
}acoral_evt_t;
void acoral_kill_thread(acoral_thread_t *thread){
acoral_evt_t *evt;
acoral_enter_critical();
if(thread->state & ACORAL_THREAD_STATE_SUSPEND)
{
evt = thread->evt;
if(thread->state & ACORAL_THREAD_STATE_DELAY){
acoral_list_del(&thread->waiting);
}else{
if(evt!=NULL){
acoral_evt_queue_del(thread);
}
}
}
acoral_unrdy_thread(thread); //将线程从就绪队列中取下
acoral_release_thread1(thread);
acoral_exit_critical();
acoral_sched();
}
如果线程处于挂起状态,则需要从相关链表中取下。
void acoral_unrdy_thread(acoral_thread_t *thread){
if(!(ACORAL_THREAD_STATE_READY&thread->state))
return;
acoral_rdyqueue_del(thread);
}
void acoral_rdyqueue_del(acoral_thread_t *thread)
{
acoral_rdy_queue_t *rdy_queue;
rdy_queue = &acoral_ready_queues;
acoral_prio_queue_del(rdy_queue, thread->prio, &thread->ready);
thread->state &= ~ACORAL_THREAD_STATE_READY;
thread->state &= ~ACORAL_THREAD_STATE_RUNNING;
thread->state |= ACORAL_THREAD_STATE_SUSPEND;
acoral_set_need_sched(true);
}
extern int daemon_id;
void acoral_release_thread1(acoral_thread_t *thread){
acoral_list_t *head;
acoral_thread_t *daem;
thread->sate = ACORAL_THREAD_STATE_EXIT;
head = &acoral_res_release_queue;
acoral_list_add2_tail(&thread->waiting, head);
daem = (acoral_thread_t *)acoral_get_res_by_id(daemon_id);
acoral_rdy_thread(daem);
}
将线程设置为退出状态,如果是当前线程,则只能是EXIT状态,表明还不能释放该线程的资源,如TCB,堆栈,因为仅管线程要退出了,还没有走到HAL_SWITCH_TO函数,该函数还需要堆栈。
void daem(void *args)
{
acoral_thread_t *thread;
acoral_list_t *head, *tmp, *tmp1;
head = &acoral_res_release_queue;
while(1)
{
for(tmp=head->next;tmp!=head;)
{
tmp1 = tmp->next;
acoral_enter_critical();
thread = list_entry(tmp, acoral_thread_t, waiting);
acoral_list_del(tmp);
acoral_exit_critical();
tmp = tmp1;
if(thread->state == RELEASE)
{
acoral_release_thread((acoral_res_t *)thread);
}else{
acoral_enter_critical();
tmp1 = head->prev;
acoral_list_add2_tail(&thread->waiting, head); /**/
acoral_exit_critical();
}
}
acoral_suspend_self();
}
}
操作系统在运行过程中,有时需要挂起某个线程,例如,当某一线程运行时需要请求某一资源,而该资源正在被其它线程所占用,此时,用户线程需要挂起自己。
void acoral_unrdy_thread(acoral_thread_t *thread){
if(!(ACORAL_THREAD_STATE_READY&thread->state))
return;
acoral_rdyqueue_del(thread);
}
void acoral_rdyqueue_del(acoral_thread_t *thread)
{
acoral_rdy_queue_t *rdy_queue;
rdy_queue = &acoral_ready_queues;
acoral_prio_queue_del(rdy_queue, thread->prio, &thread->ready);
thread->state &= ~ACORAL_THREAD_STATE_READY;
thread->state &= ~ACORAL_THREAD_STATE_RUNNING;
thread->state |= ACORAL_THREAD_STATE_SUSPEND;
/*设置线程所在的核可调度*/
acoral_set_need_sched(true);
}
void acoral_prio_queue_del(acoral_rdy_queue_t *array, unsigned char prio, acoral_list_t *list){
acoral_list_t *queue;
acoral_list_t *head;
queue = array->queue + prio;
head = queue;
array->num--;
acoral_list_del(list);
if(acoral_list_empty())
acoral_clear_bit(prio,array->bitmap);
}
任务挂起接口用到的地方很多,只要牵涉任务等待都会调用该函数。
那如何区分用户是调用acoral_suspend_thread(),还是调用acoral_delay_self()导致线程suspend的呢?
很简单,看线程TCB的waiting成员是否为空,如果因为等待时间或资源导致suspend,其waiting肯定挂在一个队列上,否则是直接调用acoral_suspend_thread()导致的suspend。
当多个线程互斥地访问某一共享资源的时候,可能导致优先级反转,优先级反转将造成实时调度算法的不确定性,进而影响系统实时性的确保。
解决优先级反转的方法是优先级继承和优先级天花板,而使用这两种方式的时候,需要动态改变线程优先级。
acoral描述线程优先级时,采用的是优先级队列,每个优先级是一个链表,因此改变优先级不是简单地将线程TCB的prio变量更改,最终要通过acoral_thread_change_prio()实现将线程挂到要设置的优先级的链表上去。
void acoral_thread_change_prio(acoral_thread_t *thread, unsigned int prio){
acoral_enter_critical();
if(thread->state&ACORAL_THREAD_STATE_READY){
acoral_rdyqueue_del(thread);
thread->prio = prio;
acoral_rdyqueue_add(thread);
}else
thread->prio = prio;
acoral_exit_critical();
}
如果线程处于就绪态,则将线程从就绪队列取下,改变优先级,再次将线程挂到就绪队列。
系统启动后,晶体振荡器源源不断地产生周期性信号,通过设置,晶体振荡器可以为系统产生稳定的Ticks,也称为心跳,Tick是系统的时基,也是系统中最小的时间单位,Tick的大小可以根据晶体振荡器的精度和用户的需求进行设置。
每当产生一个Tick,都对应着一个时钟中断服务程序ISR。
时钟中断服务程序的具体是acoral_ticks_entry()
void acoral_tciks_entry(int vector){
tick++;
if(acoral_start_sched==true){
time_delay_deal();
acoral_policy_delay_deal();
timeout_delay_deal();
}
}
acoral_list_t time_delay_queue; //线程延时队列,调用线程delay相关函数的线程都会被加到这个队列上,等待一段具体的时间后被重新唤醒
void time_delay_deal(){
acoral_list_t *tmp,*tmp1,*head;
acoral_thread_t *thread;
head = &time_delay_queue;
if(acoral_list_empty(head))
return;
thread = list_entry(head->next,acoral_thread_t,waiting);
thread->delay--;
for(tmp=head->next;tmp!=head;){
thread = list_entry(tmp,acoral_thread_t,waiting);
if(thread->delay > 0)
break;
tmp1= tmp->next;
acoral_list_del(&thread->waiting);
tmp=tmp1;
thread->state &= ~ACORAL_THREAD_STATE_DELAY;
acoral_rdy_thread(thread);
}
}
void acoral_policy_delay_deal(){
acoral_list_t *tmp,*head;
acoral_sched_policy_t *policy_ctrl;
head = &policy_list;
tmp = head;
for(tmp=head->next;tmp!=head;tmp=tmp>next)
{
policy_ctrl = list_entry(tmp,acoral_sched_policy_t,list);
if(policy_ctrl->delay_deal!=NULL)
policy_ctrl->delay_deal();
}
}
acoral_list_t period_delay_queue;//周期线程专用延时队列
void period_delay_deal()
{
acoral_list_t *tmp,*tmp1,*head;
acoral_thread_t *thread;
period_private_data_t *private_data;
head = &period_delay_queue;
if(acoral_list_empty(head))
return;
thread = list_entry(head->next, acoral_thread_t, waiting);
thread->delay--;
for(tmp=head->next;tmp!=head;){
thread = list_entry(tmp,acoral_thread_t,waiting);
if(thread->delay > 0)
break;
private_data = thread->private_data;
tmp1 = tmp->next;
acoral_list_del(&thread->waiting);
tmp = tmp1;
if(thread->state&ACORAL_THREAD_SUSPEND){
thread->stack=(unsigned int *)((char *)thread->stack_buttom+thread->stack_size-4);
HAL_STACK_INIT(&thread->stack,private_data->route,period_thread_exit,private_data->args);
acoral_rdy_thread(thread);
}
period_thread_delay(thread,private_data->time);
}
}