Homework 2 for Operating Systems class. In this assignment, we have to implement 2 algorithms:
We implemented the homework files in c++. Both problems utilize semaphores, mutexes and threads.
The barber runs on a dedicated thread, and then customers are dispatched randomly between 250 and 500 ms apart. We dispatch 20 customers, but technically it can run indefinitely. There are 2 semaphores: one to signal the barber to wake up (this also keeps track of the number of waiting customers for the barber), and one to signal to the customers that the barber is available. There is a mutex used to ensure mutual exclusion when accessing the number of available waiting chairs, as well as for tracking the total number of customers. The total number of customers is tracked so the barber knows when to leave.
In this problem and the next problem, there is an additional mutex called print_mutex.
This mutex is used to ensure that messages are printed to the terminal without other threads interrupting them, as some issues with std::cout messages being broken up were occurring.
4 threads are used (3 smokers and 1 agent). The threads lock shared resources like the ingredients (paper, matches, tobacco) and the table. The agent places resources and signals the corresponding smoker using a semaphore. Each smoker thread signals to the agent once they have finished smoking their cigarette using a semaphore, so that the agent can place two new random ingredients.
Although the table mutex isn't needed for the problem, we included one in case the problem scope ever changes (EX/ the table needs to be locked for multiple agents).
You can run both files by using our makefile, which attaches the necessary args to the command line to utilize the <semaphore.h> header.
Just run make from the base directory.
If you cannot run the makefile, you can just use the g++ arguments found in the makefile
Wayne worked on the Sleeping Barber problem, created the make file, and initialized our shared repository. Bayley worked on the Cigarette Smoker Problem. Both students went through code review of each others work, and discussed implementation with each other throughout the process.
- Wayne Stegner - stegnewe@mail.uc.edu
- Bayley King - king2b3@mail.uc.edu