What is deadlock? What causes the deadlock? Explain Semaphores, how it has controlled the race condition in operating system - Tech-n-Savvy Blogger

Deadlock:

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.

Four conditions must hold for there to be a deadlock:

Mutual exclusion condition.

Each resource is either currently assigned to exactly one process or is available.

Hold and wait condition.

Processes currently holding resources granted earlier can request new resources.

No preemption condition.

Resources previously granted cannot be forcibly taken away from a process. They must be explicitly released by the process holding them.

Circular wait condition.

There must be a circular chain of two or more processes, each of which is waiting for a resource held by the next member of the chain.

All four of these conditions must be present for a deadlock to occur. If one of them is absent, no deadlock is possible.

Explain Semaphores

Semaphores: 

Semaphore is a simply a variable. This variable is used to solve critical section problem and to achieve process synchronization in the multi-processing environment.

The two most common kinds of semaphores are counting semaphores and binary semaphores. Counting semaphore can take non-negative integer values and Binary semaphore can take the value 0 & 1. Only.