Pthreads 读写锁

▶ 使用读写锁来限制同一数据多线程读写。若任何线程拥有读锁，则其他任何请求写锁的线程将阻塞在其写锁函数的调用上；若任何线程拥有写锁，则其他任何请求读锁和写锁的线程将阻塞在其对应的锁函数上，相当于将读与写的互斥量分开，且写入锁的要求更高一些。

● 代码

 #include <stdio.h>

 #include <stdlib.h>

 #include <pthread.h>

 #pragma comment(lib, "pthreadVC2.lib")

 const int thread = , dataSize = , workCount = ;

 int data[dataSize];

 pthread_rwlock_t rwlock;

 void* work(void* rank)

 {

     const long long localRank = (long long)rank;

     int i, readCount, writeCount;

     for (i = ; i < workCount; i++)

     {

         if (rand() % )

         {

             pthread_rwlock_rdlock(&rwlock);// 读过程，上锁，读取，解锁

             data[i];

             pthread_rwlock_unlock(&rwlock);

         }

         else

         {

             pthread_rwlock_wrlock(&rwlock);// 写过程，上锁，写入，解锁

             data[i] = rand();

             pthread_rwlock_unlock(&rwlock);

         }

     }

     return nullptr;

 }

 int main()

 {

     pthread_t pth[thread];

     int i;

     long long list[thread];

     srand();

     for (i = ; i < dataSize; data[i++] = rand());

     pthread_rwlock_init(&rwlock, nullptr);  // 初始化读写锁

     for (i = ; i < thread;i++)

     {

         list[i] = i;

         pthread_create(&pth[i], nullptr, work, (void *)list[i]);

     }

     for (i = ; i < thread; i++)

         pthread_join(pth[i], nullptr);      // 销毁用完的读写锁

     pthread_rwlock_destroy(&rwlock);

     printf("\nfinish.\n");

     getchar();

     return ;

 }

● 用到的定义，pthread.h

 typedef struct pthread_rwlock_t_ * pthread_rwlock_t;

 PTW32_DLLPORT int PTW32_CDECL pthread_rwlock_init(pthread_rwlock_t *lock, const pthread_rwlockattr_t *attr);// 初始化已经声明了的读写锁，第二个参数是属性指针

 PTW32_DLLPORT int PTW32_CDECL pthread_rwlock_destroy(pthread_rwlock_t *lock);   // 销毁用完了的读写锁

 PTW32_DLLPORT int PTW32_CDECL pthread_rwlock_rdlock(pthread_rwlock_t *lock);    // 读锁定

 PTW32_DLLPORT int PTW32_CDECL pthread_rwlock_wrlock(pthread_rwlock_t *lock);    // 写锁定

 PTW32_DLLPORT int PTW32_CDECL pthread_rwlock_unlock(pthread_rwlock_t *lock);    // 解锁