/*使用读写锁实现四个线程读写一段程序的实例，共创建了四个新的线程，其中两个线程用来读取数据，另外两个线程用来写入数据。在任意时刻，如果有一个线程在写数据，将阻塞所有其他线程的任何操作。*/#include <errno.h>#include <pthread.h>#include <stdio.h>#include <stdlib.h>#include <bits/pthreadtypes.h>pthread_rwlock_t rwlock;//读写锁对象int a=0;void *thread_function_read_o(void *arg);//读线程1void *thread_function_read_t(void *arg);//读线程2void *thread_function_write_o(void *arg);//写线程1void *thread_function_write_t(void *arg);//写线程2   int main(int argc,char *argv[]){    int res;    pthread_t a_thread,b_thread,c_thread,d_thread;    void *thread_result;    res=pthread_rwlock_init(&rwlock,NULL);//初始化读写锁    if (res != 0)    {        perror("rwlock initialization failed");        exit(EXIT_FAILURE);    }    res = pthread_create(&a_thread, NULL, thread_function_read_o, NULL);//create new thread创建线程    if (res != 0)    {        perror("Thread creation failed");        exit(EXIT_FAILURE);    }     res = pthread_create(&b_thread, NULL, thread_function_read_t, NULL);//create new thread    if (res != 0)    {        perror("Thread creation failed");        exit(EXIT_FAILURE);    }    res = pthread_create(&c_thread, NULL, thread_function_write_o, NULL);//create new thread    if (res != 0)    {        perror("Thread creation failed");        exit(EXIT_FAILURE);    }    res = pthread_create(&d_thread, NULL, thread_function_write_t, NULL);//create new thread    if (res != 0)    {        perror("Thread creation failed");        exit(EXIT_FAILURE);    }        res = pthread_join(a_thread, &thread_result);//等待a_thread线程结束                if (res != 0)     {         perror("Thread join failed");         exit(EXIT_FAILURE);     }     res = pthread_join(b_thread, &thread_result);               if (res != 0)     {         perror("Thread join failed");         exit(EXIT_FAILURE);     }    res = pthread_join(c_thread, &thread_result);               if (res != 0)    {        perror("Thread join failed");        exit(EXIT_FAILURE);    }    res = pthread_join(d_thread, &thread_result);               if (res != 0)    {       perror("Thread join failed");       exit(EXIT_FAILURE);    }      res = pthread_rwlock_destroy(&rwlock);//销毁读写锁                   if (res != 0)    {       perror("rwlock destory failed");       exit(EXIT_FAILURE);    }}void *thread_function_read_o(void *arg){   pthread_rwlock_rdlock(&rwlock);//获取读取锁    printf("this is read thread1 get lock\n");      sleep(2);    printf("read thread1:%d\n",a);    pthread_rwlock_unlock(&rwlock);       pthread_exit(0);} void *thread_function_read_t(void *arg){   pthread_rwlock_rdlock(&rwlock);    printf("this is read thread2 get lock\n");    sleep(2);    printf("read thread2:%d\n",a);    pthread_rwlock_unlock(&rwlock);       pthread_exit(0);}void *thread_function_write_o(void *arg){       sleep(1);        pthread_rwlock_wrlock(&rwlock);//获取写入锁        printf("this is write thread1 get lock\n");        a++;        printf("write thread1:%d\n",a);        pthread_rwlock_unlock(&rwlock);//解锁        pthread_exit(0);}void *thread_function_write_t(void *arg){              pthread_rwlock_wrlock(&rwlock);//获取写入锁        printf("this is write thread2 get lock\n");        a+=2;        sleep(4);        printf("write thread2:%d\n",a);        pthread_rwlock_unlock(&rwlock);//解锁        pthread_exit(0);}