tests/test-progs/pthread/src/test_std_condition_variable.cpp

/*
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  * Authors: Moyang Wang
  */

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

//------------------------------------------------------------------------
// Test std::condition_variable
//------------------------------------------------------------------------
// The master thread creates N threads, each of which waits on a
// condition variable of a signal to start. The master thread then set
// the signal and notifies all other threads to begin.

#define MAX_N_WORKER_THREADS 10

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

void print_id( size_t id )
{
    std::unique_lock<std::mutex> lck(mtx);
    while (!ready)
        cv.wait(lck);
    // ...
    std::cout << "thread " << id << '\n';
}

void go()
{
    std::unique_lock<std::mutex> lck(mtx);
    ready = true;
    cv.notify_all();
}

int main( int argc, char* argv[] )
{
    size_t n_worker_threads = 0;

    std::vector< std::thread > threads;

    for ( size_t i = 0; i < MAX_N_WORKER_THREADS; i++ ) {
        try {
            threads.push_back( std::thread( print_id, i ) );
        } catch ( const std::system_error& err ) {
            break;
        }
        n_worker_threads++;
    }

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

    for (int i = 0; i < n_worker_threads; ++i) {
        threads[i].join();
    }

    // if there is no timeout (i.e., threads are all waken up properly, this
    // test always succeeds)
    return EXIT_SUCCESS;
}