菜鸟一枚，互斥锁问题

[useless1991]

//互斥锁
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <string.h>
void *fun(void *p);

int main()
{
	pthread_t pth = 0;
	pthread_mutex_t mutex;
	int ret = 0;
	char buf[50] = {0};
	
	ret = pthread_mutex_init(&mutex,NULL);
	if(0 > ret)
	{
		perror("pthread_mutex_init error");
		return 1;
	}
	ret = pthread_create(&pth,NULL,fun,&mutex);
	if(0 > ret)
	{
		perror("pthread_create error");
		return 1;
	}
	
	pthread_mutex_lock(&mutex);
	printf("this parent after 10s child\n");
	sleep(10);
	pthread_mutex_unlock(&mutex);
	
	pthread_join(pth,NULL);
	exit;
}

void *fun(void *p)
{
	pthread_mutex_t mutex = *((pthread_mutex_t *)p);
	pthread_mutex_lock(&mutex);
	printf("this is child after 5s parent\n");
	sleep(5);
	pthread_mutex_unlock(&mutex);
	pthread_exit;
}

变量mutex定义为全局变量没问题，向子线程传参就不行了，会一直等待，求解？

[mymtom]

不要拷贝MUTEX对象

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <string.h>
void *fun(void *p);
 
int main()
{
    pthread_t pth = 0;
    pthread_mutex_t mutex;
    int ret = 0;
    char buf[50] = {0};
     
    ret = pthread_mutex_init(&mutex,NULL);
    if(0 > ret)
    {
        perror("pthread_mutex_init error");
        return 1;
    }
    ret = pthread_create(&pth,NULL,fun,&mutex);
    if(0 > ret)
    {
        perror("pthread_create error");
        return 1;
    }
     
    pthread_mutex_lock(&mutex);
    printf("this parent after 10s child\n");
    sleep(10);
    pthread_mutex_unlock(&mutex);
     
    pthread_join(pth,NULL);
    exit;
}
 
void *fun_bad(void *p)
{
    pthread_mutex_t mutex = *((pthread_mutex_t *)p);
        /*
         * 不要拷贝 mutex 对象, 虽然在 FreeBSD 是可以这么做的。
         */

    pthread_mutex_lock(&mutex);
    printf("this is child after 5s parent\n");
    sleep(5);
    pthread_mutex_unlock(&mutex);
    pthread_exit;       /* 函数调用不带这么写的!!! */
}

/*
 * IEEE Std 1003.1-2008
 *
 * pthread_mutex_destroy, pthread_mutex_init - destroy and initialize a mutex
 *
 * DESCRIPTION:
 *
 * ...
 *
 * Only mutex itself may be used for performing synchronization.
 * The result of referring to copies of mutex in calls to
 * pthread_mutex_lock(), pthread_mutex_trylock(), pthread_mutex_unlock(),
 * and pthread_mutex_destroy() is undefined.
 *
 * ...
 */
void *fun(void *p)
{
    pthread_mutex_t *mutex = (pthread_mutex_t *)p;
    pthread_mutex_lock(mutex);
    printf("this is child after 5s parent\n");
    sleep(5);
    pthread_mutex_unlock(mutex);
    pthread_exit(NULL);
}

[mayer]

版主V5

[mymtom]

引用 3 楼 lunhuizhe1 的回复:

先仰慕一下版主，长姿势了又，还有我一直认为pthread_exit和exit 可以不写参数的，不写参数有什么危害呢？

你的写法不是不写参数的问题，你连括号的没有写； 不写的话就不会执行这个函数啊！exit; 是这个函数的地址. exit(0)才是这姓这个函数。

#include <stdio.h>
#include <stdlib.h>

void foo(int bar)
{
    printf("foo: bar=%d\n", bar);
}

void (*pfunc)(int);

int main(int argc, char *argv[])
{

    exit;       /* 不会执行exit(0), 实际上啥作用也没有 */

    printf("%p\n", exit);

    pfunc = foo;
    pfunc(0);   /* 相当于调用了foo(0) */

    pfunc = exit;
    pfunc(0);   /* 相当于调用了exit(0) */

    printf("%s\n", "这一行不会执行");

    return 0;
}

[useless1991]

引用 1 楼 mymtom 的回复:

不要拷贝MUTEX对象

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <string.h>
void *fun(void *p);
 
int main()
{
    pthread_t pth = 0;
    pthread_mutex_t mutex;
    int ret = 0;
    char buf[50] = {0};
     
    ret = pthread_mutex_init(&mutex,NULL);
    if(0 > ret)
    {
        perror("pthread_mutex_init error");
        return 1;
    }
    ret = pthread_create(&pth,NULL,fun,&mutex);
    if(0 > ret)
    {
        perror("pthread_create error");
        return 1;
    }
     
    pthread_mutex_lock(&mutex);
    printf("this parent after 10s child\n");
    sleep(10);
    pthread_mutex_unlock(&mutex);
     
    pthread_join(pth,NULL);
    exit;
}
 
void *fun_bad(void *p)
{
    pthread_mutex_t mutex = *((pthread_mutex_t *)p);
        /*
         * 不要拷贝 mutex 对象, 虽然在 FreeBSD 是可以这么做的。
         */

    pthread_mutex_lock(&mutex);
    printf("this is child after 5s parent\n");
    sleep(5);
    pthread_mutex_unlock(&mutex);
    pthread_exit;       /* 函数调用不带这么写的!!! */
}

/*
 * IEEE Std 1003.1-2008
 *
 * pthread_mutex_destroy, pthread_mutex_init - destroy and initialize a mutex
 *
 * DESCRIPTION:
 *
 * ...
 *
 * Only mutex itself may be used for performing synchronization.
 * The result of referring to copies of mutex in calls to
 * pthread_mutex_lock(), pthread_mutex_trylock(), pthread_mutex_unlock(),
 * and pthread_mutex_destroy() is undefined.
 *
 * ...
 */
void *fun(void *p)
{
    pthread_mutex_t *mutex = (pthread_mutex_t *)p;
    pthread_mutex_lock(mutex);
    printf("this is child after 5s parent\n");
    sleep(5);
    pthread_mutex_unlock(mutex);
    pthread_exit(NULL);
}

引用 1 楼 mymtom 的回复:

不要拷贝MUTEX对象

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <string.h>
void *fun(void *p);
 
int main()
{
    pthread_t pth = 0;
    pthread_mutex_t mutex;
    int ret = 0;
    char buf[50] = {0};
     
    ret = pthread_mutex_init(&mutex,NULL);
    if(0 > ret)
    {
        perror("pthread_mutex_init error");
        return 1;
    }
    ret = pthread_create(&pth,NULL,fun,&mutex);
    if(0 > ret)
    {
        perror("pthread_create error");
        return 1;
    }
     
    pthread_mutex_lock(&mutex);
    printf("this parent after 10s child\n");
    sleep(10);
    pthread_mutex_unlock(&mutex);
     
    pthread_join(pth,NULL);
    exit;
}
 
void *fun_bad(void *p)
{
    pthread_mutex_t mutex = *((pthread_mutex_t *)p);
        /*
         * 不要拷贝 mutex 对象, 虽然在 FreeBSD 是可以这么做的。
         */

    pthread_mutex_lock(&mutex);
    printf("this is child after 5s parent\n");
    sleep(5);
    pthread_mutex_unlock(&mutex);
    pthread_exit;       /* 函数调用不带这么写的!!! */
}

/*
 * IEEE Std 1003.1-2008
 *
 * pthread_mutex_destroy, pthread_mutex_init - destroy and initialize a mutex
 *
 * DESCRIPTION:
 *
 * ...
 *
 * Only mutex itself may be used for performing synchronization.
 * The result of referring to copies of mutex in calls to
 * pthread_mutex_lock(), pthread_mutex_trylock(), pthread_mutex_unlock(),
 * and pthread_mutex_destroy() is undefined.
 *
 * ...
 */
void *fun(void *p)
{
    pthread_mutex_t *mutex = (pthread_mutex_t *)p;
    pthread_mutex_lock(mutex);
    printf("this is child after 5s parent\n");
    sleep(5);
    pthread_mutex_unlock(mutex);
    pthread_exit(NULL);
}

先仰慕一下版主，长姿势了又，还有我一直认为pthread_exit和exit 可以不写参数的，不写参数有什么危害呢？