Which of the following is not required condition for a deadlock?

Question

Accepted Answer

The correct option is (2):
Deadlock theory, as established by the Coffman conditions, identifies four conditions that must simultaneously hold for a deadlock to occur in a system: Mutual Exclusion, Hold and Wait, No Preemption, and Circular Wait (Cycle). Therefore, the condition that is *not required* for a deadlock to happen is **Preemptive**. The actual necessary condition is **No Preemption**, which states that a resource cannot be forcibly taken away from a process; it must be released voluntarily. Since 'Preemptive' is the logical opposite of 'No Preemption', it represents a condition that actively prevents or resolves a deadlock rather than being a cause of one.

The incorrect option is (1):
Hold and Wait is a fundamental requirement for a deadlock. This condition specifies that a process must be actively holding at least one resource while simultaneously requesting and waiting for additional resources that are currently held by other processes. If a process could not hold resources while waiting, the circular dependency that leads to deadlock would be broken, as it would be forced to release its current resources before making a new request.

The incorrect option is (3):
Mutual Exclusion is a critical necessary condition. It states that at least one resource involved must be non-shareable and can only be used by one process at a time. Deadlocks cannot occur for resources that are freely shareable (like read-only files). This condition establishes the exclusive access that creates competition among processes, making a deadlock scenario physically possible.

The incorrect option is (4):
Cycle, which is shorthand for Circular Wait, is the final structural condition for a deadlock. It requires that a set of waiting processes (P0, P1, ..., Pn) must form a closed loop where each process is waiting for a resource held by the next process in the cycle, and the last process is waiting for a resource held by the first. The existence of this cycle in a resource-allocation graph is both a necessary and sufficient condition for a deadlock to exist when the other three conditions are also met.