Deadlock is a situation that occurs in OS when any process enters a waiting state because another waiting process is holding the demanded resource.

Deadlock is a situation where a set of processes 

are blocked because each process is holding a resource 

and waiting for another resource acquired by some other

process.Process 1 is holding Resource 1 and waiting for

resource 2 which is acquired by process 2, and process 2

is waiting for resource 1.

a deadlock occurs when a process or thread enters a waiting state because a requested system resource is held by another waiting process, which in turn is waiting for another resource held by another waiting process.