Concurrency:Deadlock and Starvation

In Operating Systems, concurrency refers to the ability of multiple processes to execute simultaneously, sharing common resources such as CPU time, memory, and I/O devices. However, this concurrency can lead to two major problems: Deadlock and Starvation.

Deadlock:

A deadlock is a situation where two or more processes are blocked indefinitely, each waiting for the other to release a resource. This occurs when the following four conditions are met:

1. Mutual Exclusion: Two or more processes require exclusive access to a common resource.
2. Hold and Wait: A process holds a resource and waits for another resource, which is held by another process.
3. No Preemption: The operating system cannot preempt a process holding a resource.
4. Circular Wait: A circular chain of processes exists, where each process waits for a resource held by the next process in the chain.

Starvation:

Starvation is a situation where a process is unable to gain access to a shared resource and is indefinitely postponed. This occurs when a process is waiting for a resource that is being held by another process, and the waiting process is not given a chance to execute.

Causes of Starvation:

1. Priority Scheduling: A process with a lower priority may be starved of CPU time if a higher-priority process is always running.
2. Resource Constraints: A process may be starved of a resource if another process is holding onto it for an extended period.
3. Scheduling Algorithms: Certain scheduling algorithms, such as First-Come-First-Served (FCFS), can lead to starvation.

Prevention of Deadlock and Starvation:

To prevent deadlock and starvation, operating systems use various techniques, including:

1. Resource Ordering: Ordering resources to prevent circular waits.
2. Banker's Algorithm: A resource allocation algorithm that prevents deadlock.
3. Priority Ceiling Protocol: A protocol that prevents starvation by assigning a priority ceiling to each resource.
4. Scheduling Algorithms: Using scheduling algorithms that prevent starvation, such as Round Robin (RR) and Multilevel Feedback Queue (MFQ).