How can I have a producer and consumer communicate both ways?

Question

I would like to have a worker thread wait for a command, do it, and then send the result back to the caller. This differs from the regular producer/consumer problem because of the response back.

This is what I'm thinking:

main
{
construct workers
push to shared input buffers
notify workers
wait
print results from shared output buffer
}

worker
{
wait
read from shared input buffer
do work
notify main
}

Am I on the right track? Is there a chance that the worker could respond before main starts waiting?

(I'm using C++ if that is relevant)

Answer 1

You are on the right track, but you can simplify things a bit and eliminate the need to signal or wait for signal

main
{
    push to shared input buffers
    construct workers // create and immediately run. No need for signal
    while more workers
        join worker // will block until worker thread exits
    print results from shared output buffer
}

worker
{
    read from shared input buffer
    do work
}

Depending on how you are partitioning the shared buffer, or not partitioning, you may need to protect it from concurrent writes.