condition_variable/example16.cpp

// condition_variable_any::notify_all
#include <iostream>           // std::cout
#include <thread>             // std::thread
#include <mutex>              // std::mutex
#include <condition_variable> // std::condition_variable_any

std::mutex mtx;
std::condition_variable_any cv;
bool ready = false;

void print_id (int id) {
 mtx.lock();
 while (!ready) cv.wait(mtx);
 // ...
 std::cout << "thread " << id << '\n';
 mtx.unlock();
}

void go() {
 mtx.lock();
 ready = true;
 cv.notify_all();
 mtx.unlock();
}

int main ()
{
 std::thread threads[10];
 // spawn 10 threads:
 for (int i=0; i<10; ++i)
   threads[i] = std::thread(print_id,i);

 std::cout << "10 threads ready to race...\n";
 go();                       // go!

 for (auto& th : threads) th.join();

 return 0;
}