Multi-reader-writer-with-Synchronization

IMPLEMENTATION

• I have Implemented mlti Reader Writer with synchronization (no race conditions ). The code is in C.

The main.c file handles every operation of writers and readers, the rw.c file has a client-server relationship with main.c.

The global shared queue is an array which keeps two pointers front & rear for the shared queue, each element of this shared queue can be accessed via multiple threads at the same time hence each element has locks in a form of a binary semaphore (r2_mutex) ensuring no race conditions.

Since only one write can update the queue at a certain moment a binary semaphore write_mutex which ensures no other reader or writer can access the queue at that point in time. Similarly dequeuing & enqueuing is also atomic among readers/writers hence binary semaphore deq_mutex & enq_mutex is implemented to ensure the same.

To ensure multiple readers can read a certain element concurrently, r_num is implement which stores the number of threads accessing a certain element, also r1_mutex is implemented to ensure there are no race conditions in r_num.
Main.c spawns new threads for every reader and writer and waits for user commands from rw.c.

COMPILE AND TEST

• To compile use command ‘make’
  • ./main to run the server (MUST BE STEP 1)
  • ./rw to run reader or writers
• Ensure that only one main is running.
• Once main program is running, on a new terminal run the rw program. The program can handle almost 100 readers and 100 writers.

USER INPUTS

• For writer :

  • To enqueue enter (1) followed by the element to be enqueued

  • To overwrite enter (2) followed by the index of the array to be overridden.

    $ Select Operation to be performed
     1 - overwrite data
     2 - enqueue data
    

• For reader:

  • To read a certain element from queue enter (1) followed by the index

  • To dequeue a element from queue enter (2)

    Select Operation to be performed
    1 - read data
    2 - dequeue data
    

EXPECTED OUTPUT

Once given the command the program prints out the output of the program to the corresponding terminal running it.

ERROR HANDLING

• Prompts the user if index requested for any operation is out of bounds of the queue followed by an error message
  
• Doesn’t allow writer to enqueue to a full queue.
  
• Doesn’t allow reader to dequeue an empty queue.
  
• Prompts if user enters anything other than 1 or 2 to request operations for readers and writers.