Deadlock is a situation in operating systems where two or more processes are unable to proceed because each is waiting for the other to release resources. It typically occurs in concurrent systems when multiple processes require exclusive access to shared resources such as memory, I/O devices, or files.

Deadlock is a state in a multi-process system where a set of processes are blocked because each process is holding a resource and waiting for another resource held by another process in the set. Formally, deadlock can be defined as a condition where four necessary conditions—mutual exclusion, hold and wait, no preemption, and circular wait—are all present simultaneously, leading to a system where no process can proceed. Deadlock detection, prevention, and recovery mechanisms are employed to address this issue in operating systems.

There are four necessary conditions for a deadlock to occur: mutual exclusion, hold and wait, no preemption, and circular wait. If any one of these conditions is prevented or removed, deadlock can be avoided. Deadlock prevention, avoidance, detection, and recovery strategies are employed by operating systems to handle such situations.

Common techniques to manage deadlocks include resource allocation graphs, the Banker’s algorithm for deadlock avoidance, and process termination or resource preemption for recovery. Proper synchronization and resource allocation policies help mitigate the risk of deadlocks.