Heres another combination of many things I've been trying, but still cant get this to work. Unfortunately, this only works once, meaning it only receives one dir_monitor callback event, and if I cause another same event in a monitored directory, the f_handler() callback will no longer get called. I am able to post from thread1 to thread2 or from thread1 to the main process, but that also only works one time.

Any ideas?

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boost::asio::io_service service1;
boost::asio::io_service service2;

// dir_monitor callback running in thread 1
void f_handler(const boost::system::error_code &ec, const boost::asio::dir_monitor_event &ev)
{
    TaskObj tsk = new TaskObj(...);
    // detect event, create task and post functor to thread 2 which handles tasks
    service2.post(boost::bind(&TaskObj::do_it, tsk));
}

int main(...) {
    boost::asio::dir_monitor dm(service1);
                            
    for (/*directory list*/) {
        dm.add_directory(dir);
    }
   
    dm.async_monitor(f_handler);

    // setup work to prevent exit and before running io_service
    shared_ptr<boost::asio::io_service::work>
        work(new boost::asio::io_service::work(service));

    // thread to constantly monitor dirs
    boost::thread t1 =
        boost::thread(boost::bind(&boost::asio::io_service::run,
        boost::ref(io_service)));
    t1.detach();

    // thread to do tasks as posted by dir_monitor thread and idle if no tasks exists
    boost::thread t2(boost::bind(&boost::asio::io_service::run,
        boost::ref(work_service)));
    t2.detach();

    while (true) {
        // do other stuff or idle, don't want main process to exit.
    }