thread相关——读写锁

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读写锁初始化：
int pthread_rwlock_init(pthread_rwlock_t * rwlock, const pthread_rwlockattr_t * attr);
该函数第一个参数为读写锁指针，第二个参数为读写锁属性指针。函数按读写锁属性对读写锁进行初始化。
加读锁： int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock);
该函数参数为读写锁指针。函数用于对读写锁加读锁。
加写锁：int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);
释放读写锁： int pthread_rwlock_unlock(pthread_rwlock_t *rwlock);
该函数参数为读写锁指针。函数用于释放读写锁，包括读锁与写锁。
销毁读写锁：int pthread_rwlock_destroy(pthread_rwlock_t *rwlock);
该函数参数为读写锁指针。函数用于销毁读写锁。

程序举例：
from http://blog.csdn.net/lovecodeless/article/details/24968369

#include <stdio.h>#include <Windows.h>#include <pthread.h>#include <semaphore.h>#pragma comment(lib, "pthreadVC2.lib")     //必须加上这句pthread_t t1;           //pthread_t变量t1，用于获取线程1的IDpthread_t t2;           //pthread_t变量t2，用于获取线程2的IDpthread_rwlock_t rwlock;             //声明读写锁int data=1;                          //共享资源void* readerM(void* arg){    while(1)    {    pthread_rwlock_rdlock(&rwlock);    //读者加读锁    printf("M 读者读出: %d \n",data);   //读取共享资源    pthread_rwlock_unlock(&rwlock);    //读者释放读锁    Sleep(1200);    }    return NULL;}void* readerN(void* arg){    while(1)    {    pthread_rwlock_rdlock(&rwlock);    printf(" N读者读出: %d \n",data);    pthread_rwlock_unlock(&rwlock);    Sleep(700);    }    return NULL;}void* writerA(void* arg){    while(1)    {    pthread_rwlock_wrlock(&rwlock);      //写者加写锁    data++;                              //对共享资源写数据    printf("    A写者写入: %d\n",data);    pthread_rwlock_unlock(&rwlock);      //释放写锁    Sleep(2000);    }    return NULL;}void* writerB(void* arg){    while(1)    {    pthread_rwlock_wrlock(&rwlock);     data++;    printf("    B写者写入: %d\n",data);    pthread_rwlock_unlock(&rwlock);    Sleep(2000);    }    return NULL;}void main(int argc,char** argv){    pthread_rwlock_init(&rwlock, NULL);   //初始化读写锁    pthread_create(&t1,NULL,readerM,NULL);    pthread_create(&t1,NULL,readerN,NULL);    pthread_create(&t2,NULL,writerA,NULL);    pthread_create(&t2,NULL,writerB,NULL);    pthread_rwlock_destroy(&rwlock);      //销毁读写锁    Sleep(10000);    return;}

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