Deadlock Conditions

Deadlock occurs when four necessary conditions hold simultaneously in a system. These conditions, first described by Coffman, Elphick, and Shoshani in 1971, are: 1) Mutual Exclusion - At least one resource must be held in a non-sharable mode, meaning only one process can use the resource at a time. 2) Hold and Wait - Processes already holding resources may request additional resources without releasing their current resources. 3) No Preemption - Resources cannot be forcibly taken from processes; they must be explicitly released by the process holding them. 4) Circular Wait - A circular chain of processes exists where each process is waiting for a resource held by the next process in the chain. All four conditions must be present for a deadlock to occur. If any one condition is prevented, deadlock cannot occur. Understanding these conditions is fundamental to deadlock analysis, as they provide the basis for deadlock prevention, avoidance, and detection strategies. System designers can choose which condition to target based on system requirements and constraints.