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deadlock recovery

·        Recovery by process termination

_ Terminate deadlocked processes in a systematic way

_ When enough processes terminated to recover from deadlock, stop terminations

_ Problems with the approach

_ If the process is in the midst of updating a file, its termination may leave the file in an incorrect state

_ If the process is in the midst of printing, the based on printer must be reset

_ Processes should be terminated some criterion/policy

_ Priority of a process

_ CPU time used and expected usage before completion

_ Number and type of resources being used (can they be preempted easily?)

_ Number of resources needed for completion

_ Number of processes needed to be terminated

_ Are the processes interactive or batch?

_ Minimum cost recovery

_ Cost of recovery

_ Cost of destroying a process

_ Cost of recovery from the next process state