linux多线程编程详解

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 

       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_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 

       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 

       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 

       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 

       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 

       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 
#include 
#include 
#include 
#include 

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：

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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