In a system with multiple processes and resource types, which of the following is a valid method to recover from a deadlock?

Question

In a system with multiple processes and resource types, which of the following is a valid method to recover from a deadlock?

1. A. Decreasing the CPU priority of all processes
2. B. Preempt resources from one process and allocate to another (Correct answer)
3. C. Increase the priority of all processes in the deadlock
4. D. Increase the priority of one of the processes in the deadlock

Correct Answer

Option B — B

Detailed Solution & Explanation

The correct answer is Option B.

Key Points

• preempt resources from one process and allocate to another.
• Once a deadlock exists, the operating system can recover in two broad ways: process termination (kill one or more processes) or resource preemption (forcibly take a resource from one process and give it to another to break the circular wait).
• Option B is the valid preemption method.

Additional Information

• changing process priorities (A, C, D) does nothing to break a deadlock — the processes are already blocked waiting on each other's resources, and priority does not release a held resource.

Exam Tip

• the four Coffman conditions for deadlock are mutual exclusion, hold-and-wait, no preemption, and circular wait — all four must hold, so breaking any one prevents or resolves deadlock.