C++ - How not to miss multiple notifications from multiple threads? - c++

Question

In my application, many threads notify a waiting thread. Sometimes these notifications are very close to each other in time and the waiting thread misses the notification. Is there any easy way to counter this issue? A small example code is given below. In the code, the task2 notifies the waiting thread but the waiting thread, waitingForWork, miss the notification.
#include <condition_variable>
#include <iostream>
#include <thread>
std::mutex mutex_;
std::condition_variable condVar;
bool dataReady{ false };
void waitingForWork() {
for (int i = 0; i < 2; i++)
{
std::cout << "Waiting " << std::endl;
std::unique_lock<std::mutex> lck(mutex_);
condVar.wait(lck, [] { return dataReady; });
dataReady = false;
std::cout << "Running " << std::endl;
}
}
void task1() {
std::this_thread::sleep_for(std::chrono::milliseconds{ 45 });
std::lock_guard<std::mutex> lck(mutex_);
dataReady = true;
std::cout << "Task1 Done:" << std::endl;
condVar.notify_one();
}
void task2() {
std::this_thread::sleep_for(std::chrono::milliseconds{ 46 });
std::lock_guard<std::mutex> lck(mutex_);
dataReady = true;
std::cout << "Task2 Done" << std::endl;
condVar.notify_one();
}
int main() {
std::cout << std::endl;
std::thread t1(waitingForWork);
std::thread t2(task1);
std::thread t3(task2);
t1.join();
t2.join();
t3.join();
std::cout << std::endl;
system("pause");
}

Answer 1

It's a multiple producer single consumer problem. Which is described here:
Multiple consumer single producer problem
So basically you have to change your code in a way that each thread have to write notifications into a threadsafe queue.
And then your worker thread has to work on this queue and will not miss anymore notifications.