Process Synchronization is a way to coordinate processes that use shared data. It occurs in an operating system among cooperating processes. While executing many concurrent processes, process synchronization helps to maintain shared data consistency and cooperating process execution.

The main purpose of synchronization is the sharing of resources without interference using mutual exclusion. The other purpose is the coordination of the process interactions in an operating system. Semaphores and monitors are the most powerful and most commonly used mechanisms to solve synchronization problems.

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.

1) Progress is : If no process is executing in its critical section and some processes wish to enter their critical sections, then only those processes that are not executing in their remainder section can participate in deciding which will enter its critical section next, and this selection cannot be postponed …

There are two types of semaphores:

• Binary Semaphores: In Binary semaphores, the value of the semaphore variable will be 0 or 1.
• Counting Semaphores: In Counting semaphores, firstly, the semaphore variable is initialized with the number of resources available.

Classical Problems of Synchronization

• Bounded Buffer (Producer-Consumer) Problem.
• Dining Philosophers Problem.
• The Readers Writers Problem.

Classic problems of synchronization The Producer–Consumer Problem (also called The Bounded Buffer Problem); The Readers–Writers Problem; The Dining Philosophers Problem.

Process Synchronization is the task of coordinating the execution of processes in a way that no two processes can have access to the same shared data and resources. This can lead to the inconsistency of shared data.

Sharing of information between multiple processes can be accomplished using cooperating processes. This may include access to the same files. A mechanism is required so that the processes can access the files in parallel to each other.

The two steps of a process execution are : (choose two)

• ✅ I/O Burst, CPU Burst.
• CPU Burst.
• Memory Burst.
• OS Burst.

In computer science, a semaphore is a variable or abstract data type used to control access to a common resource by multiple processes and avoid critical section problems in a concurrent system such as a multitasking operating system.

The main task of the OS is detecting the deadlocks. The OS can detect the deadlocks with the help of Resource allocation graph. In single instanced resource types, if a cycle is being formed in the system then there will definitely be a deadlock.

Deadlock recovery performs when a deadlock is detected. When deadlock detected, then our system stops working, and after the recovery of the deadlock, our system start working again. Therefore, after the detection of deadlock, a method/way must require to recover that deadlock to run the system again.

For this, we use two methods:

1. (a). Abort all the Deadlocked Processes: Aborting all the processes will certainly break the deadlock, but with a great expenses.
2. (b). Abort one process at a time untill deadlock is eliminated: Abort one deadlocked process at a time, untill deadlock cycle is eliminated from the system.

Deadlock prevention works by preventing one of the four Coffman conditions from occurring. Removing the mutual exclusion condition means that no process will have exclusive access to a resource. This proves impossible for resources that cannot be spooled. But even with spooled resources, the deadlock could still occur.

Deadlock is defined as a situation where set of processes are blocked because each process holding a resource and waiting to acquire a resource held by another process. Example: when two trains approach each other at a crossing, both shall come to a full stop and neither shall start up again until the other has gone.

Deadlock in OS is a situation where two or more processes are blocked. Conditions for Deadlock- Mutual Exclusion, Hold and Wait, No preemption, Circular wait. These 4 conditions must hold simultaneously for the occurrence of deadlock.

Two types of deadlocks can be considered: 1. Resource Deadlock. Occurs when processes are trying to get exclusive access to devices, files, locks, servers, or other resources. In Resource deadlock model, a process waits until it has received all the resources that it has requested.

2 different types

A deadlock is a situation in which two computer programs sharing the same resource are effectively preventing each other from accessing the resource, resulting in both programs ceasing to function. The earliest computer operating systems ran only one program at a time. This led to the problem of the deadlock.