CSE 531 – Distributed and Multiprocessor Operating Systems
Fall 2017
Project #3
Due Date: Oct 26th  2017
Submission instructions at end.



Please do the project in groups of 2 (mandatory).


For this project you are to write routines that implements semaphores and then use them to implement the readers/writers problem.

Step 1:

Declare a semaphore type (name it Semaphore_t) . The semaphore is a counter and a queue of TCBs. Semaphores declared/used in the end program will be of this type.

Step 2:

Implement the routines

Semaphore_t CreateSem(int InputValue) // mallocs a semaphore structure, initializes it to the InitValue and returns the pointer to the semaphore.

void P(Semaphore_t * sem)  // takes a pointer to a semaphore and performs P, i.e. decrements the semaphore, and if the value is less than zero then blocks the thread in the queue associated with the semaphore.

void V(Semaphore_t * sem)  // increments the semaphore, and if the value is 0 or negative,
then takes a PCB out of the semaphore queue and puts it into the ReadyQ.
Note: The V routine also "yields" to the next runnable thread.

-- put the code in a file called “sem.h”. Of course you need to include threads.h into this file (to get access to yield) and threads includes tcb.h.


Step 3:

Test the semaphore implementation using simple test routines. Test it more by using a producer-consumer program. (The semaphore testing program will only include sem.h, which includes the other files, transitively).  – Do NOT submit

Step 4:

Modify the p-threads implementation of readers and writers and run it with your implementation of semaphores. Submit this program.


Your project must consist of 5 files:

1.      TCB.h  (uses ucontext.h)

2.      q.h   (includes TCB.h)

3.      threads.h  (includes q.h)

4.      sem.h (includes threads.h)

5.      read_write.c – must contain your name(s) in comments @ beginning

(make sure the compile command, “gcc read_write.c” does the correct compilation).

All 5 files are to be ZIPPED into one zip or gzip file. The name of this file should reflect the name(s) of the people submitting (abbreviated, do not make it too long).

Subject MUST be “project 3”

Email the zip file to CSE531<dot>proj at gmail.