Wednesday 14 March 2012

Deadlock Characterization


Deadlock can arise if four conditions hold simultaneously.
  • Mutual exclusion:  only one process at a time can use a 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.

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