77 lines
3.2 KiB
TeX
77 lines
3.2 KiB
TeX
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% HOMEWORK #2
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% re: processes
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%
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\documentstyle[11pt,fullpage]{article}
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\pagestyle{empty}
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\begin{document}
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\begin{center}
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{\large\bf BACI Projects for an OS Course}
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\end{center}
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\begin{enumerate}
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\item {\small\bf Implementation of Machine Instructions:}
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Implement the exchange instruction in the text.
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The implementation of this instruction should be
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based on an ATOMIC function which returns a BOOLEAN value. You
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should test your implementation of the machine instruction by building
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a mutual exclusion protocol on top of your low-level operation.
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\item {\small\bf Implementation of Fair Semaphores (FIFO):}
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The default semaphore in BACI is implemented with
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a random wake up order. For non-terminating processes,
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this random behavior allows the possibility of starvation.
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A fair semaphore implementation, on the other hand,
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has a FIFO wake up order. Implement semaphores with this FIFO wake up
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order. Allow users to define a semaphore as a CONST value in the range
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[1..13]. This CONST value should be used as a tag for access to a
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semaphore and its corresponding variables.
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At least four procedures will be required in your
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implementation:
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\begin{itemize}
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\item PROCEDURE {\tt Create\_Semaphores}(); \\
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You should place your initialization code here.
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\item PROCEDURE {\tt Init\_Semaphore}({\it sem\_index} : INTEGER;
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{\it val} : INTEGER); \\
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In this procedure, you should initialize the semaphore represented by {\it
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sem\_index}. As in the given
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BACI semaphore implementation,
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your FIFO semaphore implementation should not allow the use of a
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semaphore unless it has been initialized.
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\item PROCEDURE {\tt FIFO\_P}({\it sem\_index} : INTEGER); \\
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This procedure should include the ATOMIC compare-and-swap
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operation implemented above. If a calling process needs to be put to
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sleep, use the SUSPEND operation. The WHICH\_PROC command
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helps keep track of sleeping processes.
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\item PROCEDURE {\tt FIFO\_V}({\it sem\_index} : INTEGER); \\
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This procedure should REVIVE a process waiting on the
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semaphore represented by {\it sem\_index}
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in a FIFO basis. If no such semaphore exists, this procedure should
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increment the value associated with the semaphore. Again, use the
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ATOMIC compare-and-swap operation to obtain mutual exclusive access to
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variables associated with this semaphore.
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\end{itemize}
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Bear in mind that this code should be written as a system
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implementation
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and, as such, should handle all possible errors. You are
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responsible for producing code which is robust in the presence of
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ignorant, stupid, or even malicious use by the user community.
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Lastly, full credit will not be received if your solution has
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non-required waiting.
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\item {\small\bf Implementation of Unfair Semaphores:}
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Assume that the semaphore operation given in BACI does not exist.
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Implement semaphores based on Dijkstra's original proposal by
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randomly choosing which process to wake up when a signal occurs
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(E. Dijkstra, ``Hierarchical ordering of sequential
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processes,'' {\em
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Acta Informatica}, vol. 1, no. 2, pp. 115--138, 1971.)
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The RANDOM(INTEGER) command returns a random
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number in the range [0..(INTEGER-1)].
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Follow the information in the fair semaphores implementation project on the
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minimal number of
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procedures required for this implementation.
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\end{enumerate}
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\end{document}
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