DEADLOCK

DEADLOCK CHARACTERIZATION

Deadlock can arise if four conditions hold simultaneously.

Mutual exclusion - only one process at a time can use a (non-sharable) resource.

Hold and wait - a process holding at least one resource is waiting to acquire additional resources held by other processes.

No preemption - a resource can be released only voluntarily by the process holding it, after that process has completed its task.

Circular wait - there exists a set {P0, P1, …, P0} of waiting processes such that P0 is waiting for a resource that is held by P1, P1 is waiting for a resource that is held by P2, …, Pn–1 is waiting for a resource that is held by Pn, and P0 is waiting for a resource that is held by P0.