Deadlock Detection & Avoidance

🔒 What is a Deadlock?

A deadlock is a situation in an operating system where a set of processes are blocked because each process is holding a resource and waiting for another resource acquired by another process.

🛠 Deadlock Detection

This strategy allows the system to enter a deadlock state, detect it, and then recover. It involves tracking resource allocation and identifying cycles in the resource allocation graph.

Example:

Processes: P0, P1
Resources: R0, R1

P0 holds R0 and requests R1
P1 holds R1 and requests R0

→ Deadlock detected (circular wait)

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🧠 Deadlock Avoidance

Involves careful resource allocation to ensure the system never enters an unsafe state. Banker's Algorithm is a classic example of this approach.

Banker's Algorithm Example:

Max:     P0 (7,5,3)
Alloc:   P0 (0,1,0)
Need:    P0 (7,4,3)
Available: (3,3,2)

→ System checks if resources can be safely allocated without causing a deadlock.

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📚 Key Concepts

Mutual Exclusion - Only one process can use a resource at a time.
Hold and Wait - Processes holding resources can request additional ones.
No Preemption - Resources cannot be forcibly taken.
Circular Wait - A set of processes form a circular chain of resource requests.

🔒 What is a Deadlock?