Select all of the following statements that are true An assignment edge in a resource-allocation graph points towards a process. The goal of deadlock prevention is to ensure that at least one of the four conditions necessary for deadlocks to occur is never met. A resource allocation graph is a directed graph. A cycle in a resource-allocation graph always implies the existence of a deadlock. The best approach to handle deadlocks is to apply a deadlock detection and recovery scheme. A resource allocation graph represents the resource allocation state of a system of processes and resources.

Select all of the following statements that are true An assignment edge in a resource-allocation graph points towards a process. The goal of deadlock prevention is to ensure that at least one of the four conditions necessary for deadlocks to occur is never met. A resource allocation graph is a directed graph. A cycle in a resource-allocation graph always implies the existence of a deadlock. The best approach to handle deadlocks is to apply a deadlock detection and recovery scheme. A resource allocation graph represents the resource allocation state of a system of processes and resources.

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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In operating systems or database systems, multiple processes have to access shared resources sequentially. When two or more processes are waiting for accessing shared resources circularly, a deadlock may occur that prevents the progress of all involved processes. One deadlock detection algorithm uses a “wait-for” graph to track all other processes that a process is currently blocking on. In a wait-for graph, processes are represented as nodes, and an edge from process P to Q denotes that P is waiting for a resource Q is holding. Thus a cycle in the wait-for graph shows a possibility of a deadlock. Design an efficient algorithm (pseudo code) for detecting deadlock. Analyze its complexity.
92. An edge from process Pi to Pj in a wait for graph indicates that : a. Pi is waiting for Pj to release a resource that Pi needs b. Pj is waiting for Pi to release a resource that Pj needs c. Pi is waiting for Pj to leave the system d. Pj is waiting for Pi to leave the system
Graph-theoretical treatment of deadlocks: Select all of the following statements that are true. A knot is a strongly connected subgraph of a directed graph. A process p is unblocked in a resource allocation graph if there is no request edge starting at p. In an expedient system, the resource allocation graph will never contain any satisfiable request edges. The banker's algorithm is defined for consumable resources. A knot is a necessary condition for a deadlock. In order to show that a system state is safe, the Maximum Claim Graph must be completely reducible.
Deadlocks select which is true options: a If a resource-allocation graph is expedient, a knot is a sufficient condition for deadlock. b A deadlock means that at least two processes cannot continue working because they are waiting for each other to terminate or relinquish resources. c The circular wait is one of the four conditions necessary for a deadlock to occur. d Deadlock prevention aims to abort processes or preempt some resources when deadlocks are detected. e The banker's algorithm aims to reduce the Maximum Claim Graph (MCG) completely.
5. A social graph is the representation, through a graph, of the virtual relationships that a user has within a social network. For example, in a social graph, vertices can represent users and edges can represent relationships between users. Under this concept, give a recursive definition of all users that are related to a user u in a social network.
Do the following problems:(a) Convert it to the matrix representation (i.e., Allocation, Request and Available).(b) Do a step-by-step execution of the deadlock detection algorithm. For each step, add and remove the directed edges, and redraw the resource allocation graph.(c) Is there a deadlock? If there is a deadlock, which processes are involved?
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II. Read each problem carefully and present an algorithm with the required running-time to solve each problem. 1. In class we discussed that directed acyclic graphs (DAG) can be used to represent dependency/precedence relations. One example is modeling task dependency where tasks are represented as vertices and edges represents direct dependencies between tasks, e.g., if task Ti requires task T, then there is an edge from vertex i to vertex j. Arranging tasks with respect to their dependencies can easily be done by performing topological sort to the DAG. a. Describe an algorithm that runs in O(n + m) time that given two tasks, T, and I, determines if task T, can be performed without performing task T₁. Note that I, is not required if it is not a direct or indirect dependency of T₁. Task I, is an indirect dependency of task I, if there is no edge from T, to T, but T, must appear before 7, in the topological order.
Consider the following allocation graphs G1 and G2. What can be said about the deadlock conditions? P2 R1 P1 P3 R2 P5 R3 P4 R4 Graph G1 Analyze the graphs about the deadlock conditions with justifications. Write the cycle sequence if exists. Choose one of the options given below : а. Both are deadlocked b. G1 deadlocked, G2 not С. G2 deadlocked, G1 not None of them are deadlocked d.
II. Read each problem carefully and present an algorithm with the required running-time to solve each problem. 1. In class we discussed that directed acyclic graphs (DAG) can be used to represent dependency/precedence relations. One example is modeling task dependency where tasks are represented as vertices and edges represents direct dependencies between tasks, e.g., if task Ti requires task T, then there is an edge from vertex i to vertex j. Arranging tasks with respect to their dependencies can easily be done by performing topological sort to the DAG. a. Describe an algorithm that runs in O(n + m) time that given two tasks, T₁ and T₁, determines if task T₁ can be performed without performing task Tj. Note that T; is not required if it is not a direct or indirect dependency of Ti. Task T; is an indirect dependency of task T; if there is no edge from T; to T; but I must appear before T; in the topological order. b. Describe an algorithm that runs in O(n + m) time that given a task T₁,…