Process Synchronization in Operating System (OS)

Why is Process Synchronisation Important 

When several threads (or processes) share data, running in parallel on different cores , then changes made by one process may override changes made by another process running parallel. Resulting in inconsistent data. So, this requires processes to be synchronized, handling system resources and processes to avoid such situation is known as Process Synchronization.

Classic Banking Example –

• Consider your bank account has 5000$.
• You try to withdraw 4000$ using net banking and simultaneously try to withdraw via ATM too.
• For Net Banking at time t = 0ms bank checks you have 5000$ as balance and you’re trying to withdraw 4000$ which is lesser than your available balance. So, it lets you proceed further and at time t = 1ms it connects you to server to transfer the amount
• Imagine, for ATM at time t = 0.5ms bank checks your available balance which currently is 5000$ and thus let’s you enter ATM password and withdraw amount.
• At time t = 1.5 ms ATM dispenses the cash of 4000$ and at time t = 2 net banking transfer is complete of 4000$.

Effect on the system

Now, due to concurrent access and processing time that computer takes in both ways you were able to withdraw 3000$ more than your balance. In total 8000$ were taken out and balance was just 5000$.

How to solve this Situation

To avoid such situations process synchronisation is used, so another concurrent process P2 is notified of existing concurrent process P1 and not allowed to go through as there is P1 process which is running and P2 execution is only allowed once P1 completes.

Process Synchronization also prevents race around condition. It’s the condition in which several processes access and manipulate the same data. In this condition, the outcome of the execution depends upon the particular order in which access takes place.

Types of Process Synchronization

On the basis of synchronization, processes are categorized as one of the following two types:

• Independent Process : Execution of one process does not affects the execution of other processes.
• Cooperative Process : Execution of one process affects the execution of other processes.

To understand more about process synchronization, a through understanding of process structure is required. So, let’s have a look at the elements of process .