A deadlock is a situation in which two or more competing actions are each waiting for the other to finish, and thus neither ever does.
In an operating system, a deadlock is a situation which occurs when a process enters a waiting state because a resource requested by it is being held by another waiting process, which in turn is waiting for another resource. If a process is unable to change its state indefinitely because the resources requested by it are being used by another waiting process, then the system is said to be in a deadlock.
Deadlock is a common problem in multiprocessing systems, parallel computing and distributed systems, where software and hardware locks are used to handle shared resources and implement process synchronization.
In telecommunication systems, deadlocks occur mainly due to lost or corrupt signals instead of resource contention.
Read more about Deadlock: Examples, Necessary and Sufficient Condition, Deadlock Handling, Livelock, Distributed Deadlock