Operating Systems, unit: Deadlocks. Core concepts, terminology, and worked-example cues a college student meets for this unit, building on prior units without repeating them. Front: a term, concept, or short problem cue. Back: the definition, explanation, or answer.
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- What is deadlock?
- A situation where a set of processes are each waiting for a resource held by another, with none able to proceed
- What are the four necessary conditions for deadlock, known as the Coffman conditions?
- Mutual exclusion, hold and wait, no preemption, and circular wait
- What is mutual exclusion, as a deadlock condition?
- At least one resource must be held in a non-shareable way
- What is hold and wait, as a deadlock condition?
- A process holds at least one resource while waiting for additional ones held by others
- What is no preemption, as a deadlock condition?
- Resources cannot be forcibly taken away from a process; they must be released voluntarily
- What is circular wait, as a deadlock condition?
- A cycle of processes exists, each waiting for a resource held by the next
- What is deadlock prevention?
- Designing the system so at least one of the four necessary conditions can never occur
- What is deadlock avoidance?
- Dynamically analyzing resource requests to ensure the system never enters an unsafe state
- What is the Banker's Algorithm used for?
- A deadlock avoidance algorithm that checks if granting a resource request leaves the system in a safe state
- What is a safe state, in deadlock avoidance terms?
- A state where the system can allocate resources to all processes in some order without deadlock
- What is deadlock detection?
- Allowing deadlock to occur, then periodically checking for it using resource allocation graphs
- What is a resource allocation graph?
- A diagram showing which processes hold and request which resources, used to detect deadlock cycles
- What is deadlock recovery?
- Resolving a detected deadlock, typically by terminating processes or preempting resources
- What is process termination as a deadlock recovery method?
- Killing one or more deadlocked processes to break the cycle
- What is resource preemption as a deadlock recovery method?
- Forcibly taking a resource from one process and giving it to another to break the deadlock
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