Communication: Waiting for Something

Communication between threads is often solved with polling:

• Every second, look into that data structure over there and see if something’s ready. (Only in rare occasions a mutex is used to do this, btw.)

• If response time is a requirement, continue to increase the polling interval to the point where it becomes a tight loop.

• Buy bigger batteries to power the device

Goals

• Learn which mechanisms are available to wait for something to become ready

  • Counting semaphore (as used on many bare metal OSen)

  • Condition variable