linux多线程编程详解

水深无声 2022-09-25 05:11 210阅读 0赞

**注：**如果unubtu下 man手册不全，需要安装 apt-get install manpages-posix-dev

**一、线程创建**

PTHREAD_CREATE(3)          Linux Programmer's Manual         PTHREAD_CREATE(3)
    
    NAME
           pthread_create - create a new thread
    
    SYNOPSIS
           #include <pthread.h>
    
           int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                              void *(*start_routine) (void *), void *arg);
    
           Compile and link with -pthread.

返回值：若成功，返回0；否则，返回错误编码  
参数：第二参数attr是线程的属性，可以设置为NULL使用默认属性

**二、获取线程ID**

PTHREAD_SELF(3)            Linux Programmer's Manual           PTHREAD_SELF(3)
    
    NAME
           pthread_self - obtain ID of the calling thread
    
    SYNOPSIS
           #include <pthread.h>
    
           pthread_t pthread_self(void);
    
           Compile and link with -pthread.

返回值：调用线程的线程ID

**三、线程ID比较**

PTHREAD_EQUAL(3)           Linux Programmer's Manual          PTHREAD_EQUAL(3)
    
    NAME
           pthread_equal - compare thread IDs
    
    SYNOPSIS
           #include <pthread.h>
    
           int pthread_equal(pthread_t t1, pthread_t t2);
    
           Compile and link with -pthread.

返回值：若相等，返回非0数值；否则，返回0

**四、线程终止**

PTHREAD_EXIT(3)            Linux Programmer's Manual           PTHREAD_EXIT(3)
    
    NAME
           pthread_exit - terminate calling thread
    
    SYNOPSIS
           #include <pthread.h>
    
           void pthread_exit(void *retval);
    
           Compile and link with -pthread.

**retval参数是一个无类型的指针，进程中的其他线程也可以通过调用pthread\_join访问到这个指针**

**五、阻塞等待指定线程退出**

PTHREAD_JOIN(3)            Linux Programmer's Manual           PTHREAD_JOIN(3)
    
    NAME
           pthread_join - join with a terminated thread
    
    SYNOPSIS
           #include <pthread.h>
    
           int pthread_join(pthread_t thread, void **retval);
    
           Compile and link with -pthread.

返回值：若成功，返回0；否则，返回错误编码

**注：如果线程已经处于分离状态，pthread\_join就会处于调用失败。**

**六、取消同一进程中的其他线程**

PTHREAD_CANCEL(3)          Linux Programmer's Manual         PTHREAD_CANCEL(3)
    
    NAME
           pthread_cancel - send a cancellation request to a thread
    
    SYNOPSIS
           #include <pthread.h>
    
           int pthread_cancel(pthread_t thread);
    
           Compile and link with -pthread.

返回值：若成功，返回0；否则，返回错误编码

**注：线程可以选择忽略取消或者控制如何被取消。**

**七、分离线程函数**

PTHREAD_DETACH(3)          Linux Programmer's Manual         PTHREAD_DETACH(3)
    
    NAME
           pthread_detach - detach a thread
    
    SYNOPSIS
           #include <pthread.h>
    
           int pthread_detach(pthread_t thread);
    
           Compile and link with -pthread.

返回值：若成功，返回0；否则，返回错误编码

**一个比较完整的例子，用到了上面的7个函数：gcc pthread\_create.c -pthread**

#include <pthread.h>
    #include <stdio.h>
    #include <unistd.h>
    #include <stdlib.h>
    #include <errno.h>
    
    void Perror(const char *s)
    {
        perror(s);
        exit(EXIT_FAILURE);
    }
    
    void* fun2(void *arg)
    {
        pthread_t thread_id = pthread_self();
        printf("the thread2 id is %ld, arg is %d\n", (long)thread_id, *(int*)arg);
        sleep(1); /* wait for join */
        pthread_exit((void*)2);
    }
    
    void* fun3(void *arg)
    {
        pthread_t thread_id = pthread_self();
        printf("the thread3 id is %ld, arg is %d\n", (long)thread_id, *(int*)arg);
        sleep(60); /* wait for cancel */
    }
    
    int main()
    {
        int err;
        pthread_t thread1;
        pthread_t thread2;
        pthread_t thread3;
        int arg2 = 2;
        int arg3 = 3;
    
        thread1 = pthread_self();
        printf("the thread1 id is %ld\n", (long)thread1);
    
        // Create thread
        err = pthread_create(&thread2, NULL, fun2, (void*)&arg2);
        if (err != 0) {
            Perror("can't create thread2\n");
        }
        err = pthread_create(&thread3, NULL, fun3, (void*)&arg3);
        if (err != 0) {
            Perror("can't create thread3\n");
        }
    
        // detach thread3
        err = pthread_detach(thread3);
        if (err != 0) {
            Perror("can't detach thread3\n");
        }
    
        // if equal
        if (pthread_equal(thread2, thread3) != 0)
            printf("the thread2 and thread3 same\n");
        else
            printf("the thread2 and thread3 diff\n");
    
        // wait thread2 exit
        void *retval;
        int res = pthread_join(thread2, &retval);
        if (res != 0)
            printf("can't join with thread2\n");
        else
            printf("thread2 exit code %ld\n", (long)retval);
    
        // cancel thread3
        err = pthread_cancel(thread3);
        if (err != 0) {
            Perror("can't cancel thread3\n");
        }
    
        sleep(60);
        return 0;
    }

**运行结果：**

![20160813014625608][]

注：通过pstree命令也观察到线程数如程序设置一样。

参考：《unix环境高级编程》·第三版

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[20160813014625608]: /images/20220718/7d195a6e14b94cd59112639c1227f3f8.png