4600-project-1/README.md

53 lines
2.2 KiB
Markdown
Raw Permalink Normal View History

2022-04-03 16:11:06 +00:00
# 4600-project-1
2022-05-05 06:16:11 +00:00
Project 1 for 4600
I got a grade of 101.5% :D
Please ensure you've read and agree to abide by the [license](LICENSE) before continuing.
This software's source code was made public under a restrictive license with the intent to allow comparison of Project 1 solutions with other former course-members and members of the general public. I'm not liable for any academic stupidity that may result from attempted plagiarism of this work.
You have been warned.
2022-04-06 05:20:36 +00:00
## Build
Build with `make`
Run with `make run`
Clean with `make clean`
## Explanation of Solution
### Counting Semaphores:
This project uses four counting semaphores:
* `sem_freelist` tracks the number of blocks on the `freelist`.
* This prevents any thread from trying to read a nonexistent (`nullptr`) block from the `freelist`.
* `sem_freelist_minus_1` tracks the number of blocks on the `freelist` minus 1:
* This is used to circumvent a deadlock situation where Thread-1 (the producer) will eat the last block on the `freelist` and put it on `list1`, where Thread-2 (the transformer) will never be able to consume it, since it's blocked on the empty `freelist`.
* Without this, you'd need to check that `sem_freelist > 1`, and the project specifications only allow the use of P() and V(), A.K.A. `wait()` and `signal()`.
* `sem_list1` tracks the number of blocks on `list1`.
* This prevents any thread from trying to read a nonexistent (`nullptr`) block from `list1`.
* `sem_list2` tracks the number of blocks on `list2`.
* This prevents any thread from trying to read a nonexistent (`nullptr`) block from `list2`.
All counting semaphores were used for thread synchronization.
### Binary Semaphores:
This project uses three binary semaphores:
* `sem_freelist` guarantees mutual exclusion when accessing the `freelist`.
* This prevents memory corruption, as list accesses are thread-unsafe.
* `sem_list1` guarantees mutual exclusion when accessing `list1`.
* This prevents memory corruption, as list accesses are thread-unsafe.
* `sem_list2` guarantees mutual exclusion when accessing `list2`.
* This prevents memory corruption, as list accesses are thread-unsafe.
All binary semaphores were used for mutual exclusion.