(0)deadlock characterization

Deadlock can arise if four conditions hold simultaneously:

1.Mutual Exclusion

  • only one process at a time can use a resource.
  • If another process requests that resource, the requesting process must be delayed until the resource has been released


2.Hold and Wait

  • a process that holding at least one resource is waiting to acquire additional resources held by other processes.



3.No Preemption

  • a resource can be released only voluntarily by the process holding it, after that process has completed its task.

4.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,
    P1is waiting for a resource that is held by P2, …, Pn–1is waiting for a resource that is held by Pn, and P0is waiting for a resource that is held by P0.

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