Linux系统多线程读写锁

Linux系统读写锁

实现代码

/*
author : eclipse
email  : eclipsecs@qq.com
time   : Sat May  9 16:57:24 CST 2020
*/
#include<bits/stdc++.h>
#include<unistd.h>
#include<pthread.h>
using namespace std;pthread_rwlock_t rwlock;
const int READER_NUM = 5;
int value;void* writer(void* arg) {while (true) {pthread_rwlock_wrlock(&rwlock);printf("Writer, write content %d\n", ++value);sleep(2);pthread_rwlock_unlock(&rwlock);}return (void*) 0;
}void* reader(void* arg) {while (true) {pthread_rwlock_rdlock(&rwlock);printf("Reader, read content %d\n", value);sleep(1);pthread_rwlock_unlock(&rwlock);usleep(200);}return (void*) 0;
}int main(int argc, char const * argv[]) {pthread_t readerThreadID[READER_NUM], writerThreadID;pthread_rwlock_init(&rwlock, NULL);for (int i = 0; i < READER_NUM; i++) {if (pthread_create(&readerThreadID[i], NULL, reader, NULL)) {printf("Create thread error!\n");abort();}}if (pthread_create(&writerThreadID, NULL, writer, NULL)) {printf("Create thread error!\n");abort();}for (int i = 0; i < READER_NUM; i++) {pthread_join(readerThreadID[i], NULL);}pthread_join(writerThreadID, NULL);return 0;
}

相关函数原型

pthread_rwlock_init()

  • 函数原型
    int pthread_rwlock_init(pthread_rwlock_t *restrict rwlock, const pthread_rwlockattr_t *restrict attr);
  • 参数
  1. 读写锁对象指针
  2. 读写锁属性
  • 返回值
    成功则返回0，否则返回错误代码
  • 作用
    初始化读写锁

pthread_rwlock_rdlock()

  • 函数原型
    int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock);
  • 作用
    读者锁加锁，其他写线程不能获得读写锁，读进程可以得到读写锁

pthread_rwlock_wrlock()

  • 函数原型
    int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);
  • 作用
    写者锁加锁，其他线程都不能获得读写锁

pthread_rwlock_unlock()

  • 函数原型
    int pthread_rwlock_unlock(pthread_rwlock_t *rwlock);
  • 作用
    释放读写锁，其他线程可以竞争读写锁

pthread_rwlock_destroy()

  • 函数原型
    int pthread_rwlock_destroy(pthread_rwlock_t *rwlock);
  • 参数
  1. 读写锁对象指针
  • 返回值
    成功则返回0，否则返回错误代码
  • 作用
    销毁读写锁

注意

编译过程

g++ -pthread pthreadRwlockTest.cpp -o pthreadParameterTest
./pthreadRwlockTest

注释

若注释掉读者函数中的usleep(200);会导致写者不能执行，读写锁一直被读者线程占用

输出结果

Writer, write content 1
Reader, read content 1
Reader, read content 1
Reader, read content 1
Reader, read content 1
Reader, read content 1
Writer, write content 2
Reader, read content 2
Reader, read content 2
Reader, read content 2
Reader, read content 2
Reader, read content 2
Writer, write content 3
Reader, read content 3
Reader, read content 3
Reader, read content 3
Reader, read content 3
Reader, read content 3
Writer, write content 4
Reader, read content 4
Reader, read content 4
Reader, read content 4
Reader, read content 4
Reader, read content 4

最后

  • 由于博主水平有限，不免有疏漏之处，欢迎读者随时批评指正，以免造成不必要的误解！

Linux系统多线程读写锁

Linux系统读写锁

实现代码

/*
author : eclipse
email  : eclipsecs@qq.com
time   : Sat May  9 16:57:24 CST 2020
*/
#include<bits/stdc++.h>
#include<unistd.h>
#include<pthread.h>
using namespace std;pthread_rwlock_t rwlock;
const int READER_NUM = 5;
int value;void* writer(void* arg) {while (true) {pthread_rwlock_wrlock(&rwlock);printf("Writer, write content %d\n", ++value);sleep(2);pthread_rwlock_unlock(&rwlock);}return (void*) 0;
}void* reader(void* arg) {while (true) {pthread_rwlock_rdlock(&rwlock);printf("Reader, read content %d\n", value);sleep(1);pthread_rwlock_unlock(&rwlock);usleep(200);}return (void*) 0;
}int main(int argc, char const * argv[]) {pthread_t readerThreadID[READER_NUM], writerThreadID;pthread_rwlock_init(&rwlock, NULL);for (int i = 0; i < READER_NUM; i++) {if (pthread_create(&readerThreadID[i], NULL, reader, NULL)) {printf("Create thread error!\n");abort();}}if (pthread_create(&writerThreadID, NULL, writer, NULL)) {printf("Create thread error!\n");abort();}for (int i = 0; i < READER_NUM; i++) {pthread_join(readerThreadID[i], NULL);}pthread_join(writerThreadID, NULL);return 0;
}

相关函数原型

pthread_rwlock_init()

  • 函数原型
    int pthread_rwlock_init(pthread_rwlock_t *restrict rwlock, const pthread_rwlockattr_t *restrict attr);
  • 参数
  1. 读写锁对象指针
  2. 读写锁属性
  • 返回值
    成功则返回0，否则返回错误代码
  • 作用
    初始化读写锁

pthread_rwlock_rdlock()

  • 函数原型
    int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock);
  • 作用
    读者锁加锁，其他写线程不能获得读写锁，读进程可以得到读写锁

pthread_rwlock_wrlock()

  • 函数原型
    int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);
  • 作用
    写者锁加锁，其他线程都不能获得读写锁

pthread_rwlock_unlock()

  • 函数原型
    int pthread_rwlock_unlock(pthread_rwlock_t *rwlock);
  • 作用
    释放读写锁，其他线程可以竞争读写锁

pthread_rwlock_destroy()

  • 函数原型
    int pthread_rwlock_destroy(pthread_rwlock_t *rwlock);
  • 参数
  1. 读写锁对象指针
  • 返回值
    成功则返回0，否则返回错误代码
  • 作用
    销毁读写锁

注意

编译过程

g++ -pthread pthreadRwlockTest.cpp -o pthreadParameterTest
./pthreadRwlockTest

注释

若注释掉读者函数中的usleep(200);会导致写者不能执行，读写锁一直被读者线程占用

输出结果

Writer, write content 1
Reader, read content 1
Reader, read content 1
Reader, read content 1
Reader, read content 1
Reader, read content 1
Writer, write content 2
Reader, read content 2
Reader, read content 2
Reader, read content 2
Reader, read content 2
Reader, read content 2
Writer, write content 3
Reader, read content 3
Reader, read content 3
Reader, read content 3
Reader, read content 3
Reader, read content 3
Writer, write content 4
Reader, read content 4
Reader, read content 4
Reader, read content 4
Reader, read content 4
Reader, read content 4

最后

  • 由于博主水平有限，不免有疏漏之处，欢迎读者随时批评指正，以免造成不必要的误解！