Deadlock vs Starvation in OS

Deadlock and starvation are two different process-scheduling problems. In a deadlock, processes wait forever because each is holding a resource the other needs. In starvation, some processes wait indefinitely because higher-priority processes monopolise resources.

Deadlock

Deadlock is a condition in an operating system where two or more processes are permanently blocked because each process is waiting for a resource that is held by another process, forming a circular waiting chain, and none of them can proceed.

The 4 conditions for Deadlock:

1. Mutual Exclusion → Resources cannot be shared.
2. Hold and Wait → A process holds one resource and waits for another.
3. No Preemption → Resources cannot be forcibly taken back.
4. Circular Wait → A circular chain of processes waiting.

Example:

Two cars on a narrow bridge:

• Car A enters from left → blocks Car B
• Car B enters from right → blocks Car A
  Both need the other to move back, but neither can → Deadlock.

Starvation

Starvation is a state that prevents lower-precedence processes from getting the resources. Starvation arises when procedures with critical importance keep on utilizing the resources frequently. Starvation can be cured using a technique that is regarded as aging.

In aging, priority of process increases with time and thus guarantees that poor processes will equally run in the system. 

The 4 common causes:

1. Priority-Based Scheduling – cause of starvation
2. Indefinite Blocking – cause of starvation
3. Continuous High-Priority Arrival – cause of starvation
4. Unequal Resource Allocation – cause of starvation

Example:

CPU Scheduling in a Server

• A server uses priority scheduling to handle tasks.
• If high-priority requests keep coming from premium users, low-priority tasks (free users) may never get CPU time → Starvation.