Question Answer

Deadlock: Four Necessary Conditions (Operating Systems)

• Mutual Exclusion:

  At least one resource is non-shareable. Only one process can use that resource at a time, so others must wait.

• Hold and Wait:

  A process is holding one or more resources while simultaneously requesting additional resources that are currently held by other processes.

• No Preemption:

  Resources cannot be forcibly taken away. A resource is released only when the process finishes using it and does so voluntarily.

• Circular Wait:

  There exists a circular chain of processes where each process is waiting for a resource held by the next process in the cycle (e.g., P1 waits for P2, P2 waits for P3, …, Pn waits for P1).

All four conditions must hold simultaneously for a deadlock to occur. Breaking any one of them prevents deadlock in an operating system.