Question

我是C语言和Linux的新手，英语不是我的母语。提前对不起。

我正在研究在Linux上实现循环调度程序的学校项目，我在实现调度程序和thread_self方面遇到了一些问题。

调度程序首先检查就绪队列是否为空，如果是，则设置时间片和警报（时间片）。否则，从就绪列表中查找新线程，调度新线程的TCB，设置时间片，上下文切换到新线程并设置警报（timeslice）。但是我在某些时候仍然遇到错误，我找不到要修复的地方。

另一件事是关于thread_cancel。 int thread_cancel（thread_t tid）函数删除目标tcb，我需要使用tid找到tcb。我试过像

Thread* temp = getpid();
kill(pid, SIGKILL);

但我无法弄清楚如何从队列中删除tcb。请给我一些更好的主意！

Thread.h

typedef struct _Thread{
    ThreadStatus status;
    pid_t pid;
    Thread* pPrev;
    Thread* pNext;
}Thread;
Thread* ReadyQHead;
Thread* ReadyQTail;

-Queue

typedef struct _queue{
    Thread* head;
    Thread* tail;
    unsigned int num;
} queue;

queue* runList;
queue* readyList;
queue* waitList;

-Queue.c

void enqueue(queue * q, Thread* tcb)
{
    if(q->num == 0) {
        q->head = tcb;
        q->tail = tcb;
    } else {
        q->tail->pNext = tcb;
        q->tail = tcb;
    }
    q->num ++;
}

Thread * dequeue(queue * q)
{
    Thread * tmp;
    if(q->num == 0) return NULL;
    else if(q->num == 1) {
        tmp = q->head;
        q->head = NULL;
        q->tail = NULL;
    } else {
        tmp = q->head;
        q->head = q->head->pNext;
    }
    q->num --;
    return tmp;
}

-Scheduler

void alarmHandler(int signal)
{
    printf("Scheduler awake!!");
    /*Do schedule*/
}

int RunScheduler( void )
{
    //check if ready queue is empty
    if(is_empty(readyList) != 0)
    {
        printf("this is weird");
        signal(SIGALRM, alarmHandler);
    }
    else {
        /*Look up a new thread from ready list*/
        Thread* tmp = ReadyQHead;

        /*send sigcont*/
        kill(tmp->pid, SIGCONT);

        //dispatch TCB of new thread
        if(is_empty(runList) != 0 && runList->head->status == 0)
            enqueue(readyList, tmp);

        //pick thread at head of ready list as first thread to dispatch
        tmp->status = 0; // tmp == runningTcb
        printf("alive tcb : %d\n", tmp->pid);

        ReadyQHead = dequeue(readyList);
        //set timeslice
        signal(SIGALRM, alarmHandler);
        //context switch to new thread
        _ContextSwitch(tmp->pid, ReadyQHead->pid);

    }

    while(1){
        alarm(TIMESLICE);
    }

    return 0;
}


void _ContextSwitch(int curpid, int tpid)
{
    kill(curpid, SIGSTOP);
    kill(tpid, SIGCONT);
}

实现线程调度程序循环和线程取消

0 个答案: