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13 Cards in this Set
- Front
- Back
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From an Operating System's perspective, what is the di fference between a process and a thread?
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A process is what owns the memory and is actually allocated process specific resources from the operating system. A thread is a trace through an application. Shares the memory of process with every other thread in a process
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What are some of the benefi ts of threads?
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faster to create and terminate
faster to switch between two threads more efficient communication between threads parellel processing |
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What are two ways that a semaphore can be used? Give an example of each.
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Mutex:
Condition Variable |
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How do semaphores compare to mutexes?
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A semaphore is a generalized version of a mutex. A semaphore can be used as a mutex, but it can also be used as a condition variables.
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How do semaphores compare to condition variables?
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A semaphore is a generalized version of a condition variable. A semaphore can be used as a condition variable, but it can also be used as a mutex variables.
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What is the diff erence between a Hoare monitor and a Lampson Redell monitor?
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A Hoare monitor uses c_signal and so only awakens one waiting process at a time. Does not require rechecking of conditions. A Lampson Redell Monitor uses c_signal and can allow a process to reawaken even though the condition may have changed. Requires the condition rechecking
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Explain how can you emulate a monitor using semaphores.
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You place all data as private members of a class. That class uses the a single semaphore, with the semaphores inside the methods not outside. Use while loops to recheck conditions and semaphores acting as condition variables to signify cwait and csignal
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Explain how you could use a central mailbox to provide mutual exclusion among a set of dis-
tributed threads using message passing. |
Create one thread that is used by all threads. All threads pass messages to the mailbox and poll it to get responses. Use a null message as a key and block if the key isn't available
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1st deadlock
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Mutual exclusion: only one thread may use a resource at a time
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2nd deadlock
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hold and wait: a thread holds one resource while waiting for another
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3rd deadlock
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no preemption: a thread can't be forced to release a resource
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4th deadlock
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circular wait: a cycle of threads waiting for each other
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2 ways to prevent a deadlock
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prevent hold and wait: a thread can only hold one resource at a time
prevent circular wait: impose ordering on resources |
