多线程编程，线程同步，线程互斥示例

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>
int count,v1,v2;
int flags = 1;
sem_t sem;
pthread_mutex_t mt;
void *fun(void *arg)
{
    int ret = -1;
    while(1)
    {
#if 0
        ret = sem_wait(&sem);
        if ( -1 == ret )
        {
            perror("sem_init");
            return ;
        }
#else
        ret = pthread_mutex_lock(&mt);
        if (0 != ret)
        {
            perror("pthread_mutex_lock");
            return -1;
        }

#endif
        if ( v1 != v2 )
            printf("******* %d,%d
",v1,v2);
#if 0
        ret = sem_post(&sem);
        if ( -1 == ret )
        {
            perror("sem_init");
            return ;
        }
#else
        ret = pthread_mutex_unlock(&mt);
        if (0 != ret)
        {
            perror("pthread_mutex_lock");
            return -1;
        }
#endif
    }
    *((int *)arg) = 3;
    pthread_exit("fun");//exit
}
int main(int argc,char **argv)
{
    int a = 0;
    pthread_t id;
    int ret = -1;
    void * val = NULL;
#if 0
    ret = sem_init(&sem,0,1);
    if ( -1 == ret )
    {
        perror("sem_init");
        return -1;
    }
#else  
    ret = pthread_mutex_init(&mt,NULL);
    if( 0 != ret)
    {
        perror("pthread_mutex_init");
        return -1;
    }
#endif
    ret = pthread_create(&id,NULL,fun,(void*)&a);//fork
    if ( 0 != ret )
    {
        perror("pthread_creat");
        return -1;
    }

    while(1)
    {
#if 0
        ret = sem_wait(&sem);
        if ( -1 == ret )
        {
            perror("sem_init");
            return -1;
        }
#else 
        ret = pthread_mutex_lock(&mt);
        if (0 != ret)
        {
            perror("pthread_mutex_lock");
            return -1;
        }
#endif
        count++;
        v1=count;
        v2=count;
#if 0
        ret = sem_post(&sem);
        if ( -1 == ret )
        {
            perror("sem_init");
            return -1;
        }
#else 
        ret = pthread_mutex_unlock(&mt);
        if (0 != ret)
        {
            perror("pthread_mutex_lock");
            return -1;
        }
#endif
    }
    ret = pthread_join(id,&val);//wait
    if ( 0 != ret )
    {
        perror("pthread_join");
        return -1;
    }
    printf("return val is %s
",val);
    printf("%d**
",a);
    return 0;
}