Block a worker thread until data is present

[MAKennedy]

Hi all!

My apologies to you in my ignorance.  I'm a Linux developer.

I have a worker thread that I need to run wide open.  If, however, there is nothing for it to do, I need it to sleep until an asynchronous event turns it back on.  In Linux, I might do something like:

wait_queue_head_t wq;
atomic_t data_present = ATOMIC_INIT(0);
int main(void)
{
        init_waitqueue_head (&wq);
        // Create the worker_thread
        // Provide the callback for the async event
        // wait for some event to make us return.
        return 0;
}

int isr_callback(<whatever>)
{
        // Handle the event, and post the data for the worker thread
        atomic_set(data_present, 1);
        wake_up(wq);
}
void worker_thread()
{
        while (!stop_worker_thread){
                wait_event(wq, atomic_read(data_present));
                // work the data.
                atomic_set(data_present, 0);
        }
}

How do I achieve the same thing in LabWindows?  To be more wordy:  I want to generate a thread that handles LOADS of information.  However, if the system goes dark for a bit, I don't want that thread to spin but rather sleep waiting on someone else (the ISR) to wake it up.  Also, given the bulk of the data coming in, creating a thread on the fly would overload the system and would cause the application to crash -- so, I need only one thread to react to an async event that I can then wake up on to process data.

Hope this is a clear question.

Thanks in advance for any direction you can provide!

Andy

[MAKennedy]

If you have stumbled across this thread and were hoping to find the answer, the best I came up with after an all day search was <https://docs.microsoft.com/en-us/windows/win32/sync/using-condition-variables>.  This appears to be the "right way" to do it.

[RobertoBozzolo]

You're right, your application seems to fit well in the producer-consumer paradigm. If you want to explore this way you could benefit by using the Tread-Safe Queues that CVI offers in the Utility library: until the producer does not input data in the queue the consumer thread is idle and consumes no system resources.

I suggest you to read Creating Applications >> Creating Multithreaded Applications chapter in CVI help where the thread safe queue mechanism is described, and the examples that you can find searching for Queue in the Example Finder (Help >> Find Examples...)