Problem 3 A precedence graph is a directed, acyclic graph. Nodes represent tasks

Question

Problem 3 A precedence graph is a directed, acyclic graph. Nodes represent tasks, and arcs indicate the order in which tasks are to be accomplished. In particular, a task can execute as soon as its predecessors have been completed. Assume that the tasks are processes and that each process has the following outline: Process T Wait for predecessors, if any Body of the task; Signal successors, if any; Using semaphores, show how to synchronize five processes whose permissible execution order is specified by the following precedence graph: I1 113 T3 Do not impose constraints that are not specified in the graph. For example, T2 and T3 can execute concurrently after T1 completes. Answer:

Explanation / Answer

Process T1{

No wait, as it is the first task to execute;

Execute T1;

Signal T2 and T3 to execute;

}

Process T2{

Wait for process T1 to complete its execution

Execute T2;

Signal T4 for execution;

}

Process T3{

Wait for process T1 to complete its execution

Execute T3;

Signal T5 to execute;

}

Process T4{

Wait for process T2 to complete its execution

Execute T4;

Signal T5 to execute;

}

Process T5{

Wait for process T3 and T4 to complete their execution

Execute T5;

No signal, because its last task;

}

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