使用 notify_one() 向正在运行的线程发出多个 std::condition_variable 通知

Question

我正在尝试使用 std::condition_variable 从另一个线程（主线程）向正在运行的线程发送多个通知。发送一次有效，但第二次或多次发送似乎不起作用。这就是我所做的（没有实际事件的不必要细节）：

#include <iostream>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <future>

bool keep_running=true;
bool condition_reached=false;
std::mutex cond_mtx;
std::condition_variable cond;

void thread_waiting_to_be_notified(){
    while(keep_running){
        std::unique_lock<std::mutex> lk(cond_mtx);
        cond.wait(lk,[]()->bool{return condition_reached;});
        std::cout << "got notitication" << std::endl;
        condition_reached=false;
   }
}

void some_event(){
/*some event happens here*/
}

void another_event(){
/*another event happens here*/
}

int main(){
    std::thread thr(thread_waiting_to_be_notified);

    some_event();//first event
    std::cout << "some event happened" << std::endl;
    condition_reached=true;
    cond.notify_one();

    another_event();//second event
    std::cout << "another event happened" << std::endl; 
    condition_reached=true;
    cond.notify_one();
    keep_running=false;
    thr.join();

     return 0;
}

---

我得到的输出

some event happened
another event happened
got notitication

不过，我希望

some event happened
another event happened
got notitication
got notitication

任何建议将不胜感激。

Answer 1

尝试在后面插入lk.unlock();

condition_reached=false;