Deadlock Prevention Deadlock Prevention
„ - Mutual Exclusion – not required for sharable resources; must hold for nonsharable
resources.
„ - Hold and Wait – must guarantee that whenever a process requests a resource, it
does not hold any other resources.
· Require process to request and be allocated all its resources before it begins
execution, or allow process to request resources only when the process has
none.
· Low resource utilization; starvation possible
„
- No Preemption –
· If a process that is holding some resources requests another resource that
cannot be immediately allocated to it, then all resources currently being held
are released.
· Preempted resources are added to the list of resources for which the process is
waiting.
· Process will be restarted only when it can regain its old resources, as well as
the new ones that it is requesting.
- „Circular Wait – impose a total ordering of all resource types, and require that each
process requests resources in an increasing order of enumeration.
Restrain the ways that request can be made.
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