Background
I am somewhat confused about my understanding of how condition variables operate in conjunction with concurrent access to shared data. The following is pseudo code to depict my current issue.
// Thread 1: Producervoid cakeMaker(){ lock(some_lock); while(number_of_cakes == MAX_CAKES) wait(rack_has_space); number_of_cakes++; signal(rack_has_cakes); unlock(some_lock);}// Thread 2: Consumervoid cakeEater(){ lock(some_lock); while(number_of_cakes == 0) wait(rack_has_cakes); number_of_cakes--; signal(rack_has_space); unlock(some_lock);}Let's consider the scenario where the value of number_of_cakes is 0. As a result, Thread 2 is blocked at wait(rack_has_cakes). When Thread 1 runs and increments the value of number_of_cakes to 1, it signals rack_has_cakes. However, Thread 2 wakes up before Thread 1 releases the lock on some_lock, causing it to go back to sleep and miss the signal.
I am unclear about the operation of wait and signal. Are they like a toggle switch that gets set to 1 when signal is called and 0 when wait succeeds? Can someone explain what is happening behind the scenes?
Question
Can someone walk me through one iteration of the above code step-by-step, with a strong emphasis on the events that occur during the signal and wait method calls?
