读写锁

/*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1

void *thread_function_read_t(void *arg);//读线程2

void *thread_function_write_o(void *arg);//写线程1

void *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); }