Cs162_fa08_mt1-11 - can make no further progress Explain how each of the four conditions of deadlock are satisfied by your example Hint Links are

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CS 162 Fall 2008 Midterm Exam I October 15, 2008 Page 13/21 Problem 4: Deadlock[21 pts] Problem 4a[5pts]: The figure at the right illustrates a 2D mesh of network routers. Each router is connected to each of its neighbors by two network links (small arrows), one in each direction. Messages are routed from a source router to a destination router and can stretch through the network (i.e. consume links along the route from source to destination). Messages can cross inside routers. Assume that no network link can service more than one message at a time, and that each message must consume a continuous set of channels (like a snake). Messages always make progress to the destination and never wrap back on themselves. The figure shows two messages (thick arrows). Assume that each router or link has a very small amount of buffer space and that each message can be arbitrarily long. Show a situation (with a drawing) in which messages are deadlocked and
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Unformatted text preview: can make no further progress. Explain how each of the four conditions of deadlock are satisfied by your example. Hint: Links are the limited resources in this example. Problem 4b[3pts]: Define a routing policy that avoids deadlocks in the network of (4a). Name one of the four conditions that is no longer possible, given your routing policy. Explain. Problem 4c[3pts]: Suppose that each router node contains sufficient queue space to hold complete messages (assume infinite space, if you like). Why is it impossible for deadlocks such as in (4a) to occur? Name one of the four conditions that is no longer possible, given infinite queue space in the router. Explain. R R R R R R R R R R R R R R R R...
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This note was uploaded on 08/26/2009 for the course CS 162 taught by Professor Kubiatowicz during the Spring '02 term at University of California, Berkeley.

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