为什么我的线程永远不会结束

Question

我想要实现使用C++ 11.It是一个work_queue，工人和功能可按线程的向量组成的模板类线程池。这里是我的h文件

#ifndef THREADPOOL_H 
#define THREADPOOL_H 

#include <vector> 
#include <list> 
#include <memory> 
#include <thread> 
#include <mutex> 
#include <condition_variable> 

// a threadpool with template 
template<typename T> 
class threadpool { 
public: 
    threadpool(int thread_num, int request_num); 
    bool add_requests(T* request); 
    void run(); 
    ~threadpool(); 

private: 
    //the vector of multiple thread 
    std::vector<std::thread> threads; 
    // the task queue 
    std::list<T*> work_queue; 

    //synchronization 
    std::mutex queue_mutex; 
    std::condition_variable condition; 
    int max_requests; 
    bool stop; 


}; 

//the worker function 
template<typename T> 
void threadpool<T>::run() { 
    while (1) { 
     T* request; 
     { 
      std::unique_lock<std::mutex> lock(this->queue_mutex); 
      condition.wait(lock, [this] {return !(this->work_queue.empty()); }); 
      if (this->stop&&this->work_queue.empty()) 
       return; 
      request = work_queue.front(); 
      work_queue.pop_front(); 
     } 
     request->process(); 
    } 
} 

//add new work item to the pool 
template<typename T> 
bool threadpool<T>::add_requests(T* request) { 
    std::unique_lock<std::mutex> lock(this->queue_mutex); 
    if (work_queue.size() >= max_requests) 
     return false; 
    work_queue.push_back(request); 
    condition.notify_one(); 
    return true; 
} 
// the constructor 
template<typename T> 
inline threadpool<T>::threadpool(int thread_num, int request_num) :max_requests(request_num), stop(false) { 
    for (int i = 0; i < thread_num; ++i) 
     threads.emplace_back(&threadpool::run, this); 

} 

// the destructor joins all threads 
template<typename T> 
inline threadpool<T>::~threadpool() 
{ 
    { 
     std::unique_lock<std::mutex> lock(queue_mutex); 
     stop = true; 
    } 
    condition.notify_all(); 
    //there is an error, the thread never stops... 
    for (std::thread &worker: threads) 
     worker.join(); 
} 

#endif 

而我的测试代码如下。有一些错误。人们似乎对我的Thread.join死锁（），可以在任何一个可以告诉我为什么吗？当你在析构函数设置stop到true

//for test my thread pool 
#include"threadpool.h" 
#include<iostream> 
#include<ctime> 
#include <windows.h> 

struct node { 

    static int cur; 
    void process(){ 
     ++cur; 
     std::cout << cur << std::endl; 
     Sleep(2000); 
    } 
}; 

int node::cur = 10; 

int main() 
{ 
    threadpool<node> haha(4, 5); 
    clock_t start; 
    clock_t end; 
    node a1; 
    node a2; 
    node a3; 
    //start = clock(); 
    //add request 
    haha.add_requests(&a1); 
    haha.add_requests(&a2); 
    haha.add_requests(&a3); 
    return 0; 

} 

Answer 1

你的条件变量断言可能不会打破观望，所以你应该检查stop里面还有：

condition.wait(lock, [this] {return this->stop || !(this->work_queue.empty()); });