Term
| What are the 5 process states? |
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Definition
| New, Running, Waiting, Ready, and Terminated |
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Term
| What is the Process Control Block (PCB)? |
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Definition
| It is a piece of memory that has info about a process including state, program counter, CPU registers, CPU scheduling info, memory management info, accounting info, and I/O status. |
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Term
| Name 3 pieces of information contained in a PCB |
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Definition
- process state
- program counter
- CPU registers
- CPU scheduling info
- memory management info
- accounting info
- I/O status
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Term
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Definition
| a list of all the processes in the system |
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Term
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Definition
| a list of all the processes ready and waiting to execute |
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Term
| What is the Device Queue? |
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Definition
| a list of processes waiting for a particular I/O device. |
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Term
| What is an I/O Bound Process? |
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Definition
| a process that spends most of its time doing I/O |
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Term
| What is a CPU Bound Process? |
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Definition
| a process that spends most of its time doing computations |
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
| What does the exec() command do in Unix/C? |
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Definition
| It is a system call that replaces the current executable with a new executable. |
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Term
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Definition
| A situation where a waiting process is never again able to change state because resources it needs are held by other waiting processes. |
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Term
| What are the three steps that occur in the normal mode of operation when a process wants to utilize a resource? |
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Definition
1. Request the resource (waiting if not available)
2. Use the resource (exclusively)
3. Release the resource (so others can use it) |
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Term
| What are the 4 conditions that must hold for a deadlock? |
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Definition
1. Mutual Exclusion - nonsharable resource held
2. Hold and Wait - a process is holding a resource and waiting on another resource
3. No Preemption - a process can only be interrupted/prempted by itself (after completion)
4. Circular Wait - the hold and wait chain is circular |
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Term
| Resource Allocation Graph |
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Definition
| Know about the resource allocation graph in 7.2.2. It allows you to check for deadlocks. |
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Term
| Three General Approaches to Handling Deadlocks |
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Definition
1. Use protocol to prevent or avoid deadlocks
2. Allow a system to deadlock, detect it, and then recover
3. Ignore the problem and hope deadlocks never occur |
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Term
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Definition
| Generally speaking, tries to ensure that at least on of the 4 deadlock conditions cannot hold. |
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Term
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Definition
| Generally speaking, the OS basically requires that processes tell in advance what resources they will need during their lifetime. This information can then be used to schedule the processes to avoid a deadlock. |
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Term
| Can the denial mutual exclusion be used for deadlock prevention? |
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Definition
| No, because some resources are intrinsically nonsharable and need mutual exclusion. |
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Term
| Can we prevent hold and wait from ever occurring to prevent deadlock? |
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Definition
| Yes, two ways are to either force a process to request all (or none) resources before execution or make a process release its current resources before requesting more. |
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Term
| How can the denial of 'No Preemption' be used to prevent deadlock? |
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Definition
| If a process is holding some resources and requests another resource that isn't available, then this process will be preempted. Similarly, if a process needs resources that a process who is waiting has, then that other process can be prempted of its resources. |
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Term
| Can the denial of the 'Circular Wait' condition be used to prevent deadlock? |
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Definition
| Yes, by imposing a total ordering on resource types and then requiring that processes request resources in that ordering. |
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Term
| Safe State (in the context of deadlock avoidance) |
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Definition
| A state is safe if the system can allocate resources to each process (up to its maximum) in some order and still avoid a deadlock. |
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Term
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Definition
| A system is in a safe state if there is a safe sequence. A safe sequence is a sequence of processes that can execute given the current allocation of resources and the newly released resources of the processes that execute before it. |
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Term
| Resource Allocation Graph Algorithm |
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Definition
| This is in section 7.5.2, it is a variation of the resource allocation graph that allows for deadlock avoidance by adding a claim edge (dotted directed edge) for future resource needs of a process. |
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Term
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Definition
| You have the matrices: available, max, and allocation. You need to comput the matrix: Need by doing (Max - Allocation). |
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Term
| Deadlock Detection Algorithm |
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Definition
| You have matrices: available, allocation, and request. You then calculate a vector, Finish, by checking if the request can be satisfied by the available. |
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