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PROCESS SYNCHRONIZATION, PRODUCER CONSUMER PROBLEM, PETERSON'S…

- - - - Locks
        
        A mutex is a locking mechanism used to synchronize access to the resource. There is ownership associated with the mutex
        
        Only one task(Process or Thread) can acquire the mutex
        
        Only the owner can release the lock(mutex)
      - Semaphores
        
        A semaphore is a signaling mechanism
        (Hey I am done you can carry on type signal)
      - Atomic Operations
        
        Atomicity refers to a operation or a sequence of operations that are guaranteed to execute as a single, indivisible unit of work without any possibility of interference from other operations.
        In other words these operations can not be interrupted or partially completed
      - NECESSARY CONDITIONS
        
        PROGRESS
        
        a process outside the critical section should not block other processes from entering the critical section.
        
        BOUNDED WAITING
        
        There should be no infinite amount of waiting for thread, there should be bounded waiting such that after waiting for that period the thread should be allowed to enter the crtitical section
        
        MUTUAL EXCLUSION
        
        if a process is executing in its critical section, then no other process is allowed to execute in the critical section.
- - - - Tracks the spaces filled by the Producer Process
        initialized to 0 at the beginning
    - - Tracks the empty spaces in the buffer
        Initialized to BUFFER_SIZE
    - - Used for mutual exclusion so that only one process gets access to the shared buffer at a time.

PETERSON'S SOLUTION

while(1)
{

    flag[1] = T
    turn = 0

    while(turn == 0 && flag[0] == T)
    {

        /// CRITICAL SECTION

        flag[1] == F


    }
}

while(1)
{

    flag[0] = T
    turn = 1

    while(turn == 1 && flag[1] == T)
    {

        /// CRITICAL SECTION

        flag[0] == F


    }
}

- - - - It will create a Deadlock
        
        Solutions
        
        Odd - Even Rule
        an odd phi. first takes his left fork and then his right fork whereas an even phi. first takes his right fork first and then his left fork
        
        Allow a phi. to pick up his fork only when both the forks are available and to do this, he must pick them up in a critical section (atomically).
        
        Only 4 philosophers are allowed to sit simultaneously.