# Recent questions tagged tanenbaum

1
In certain countries, when two people meet they bow to each other. The protocol is that one of them bows first and stays down until the other one bows. If they bow at the same time, they will both stay bowed forever. Write a program that does not deadlock.
2
Write a program that detects if there is a deadlock in the system by using a resource allocation graph. Your program should read from a file the following inputs: the number of processes and the number of resources. For each process if should read four numbers: the ... is a deadlock in the system. In case there is, the program should print out the identities of all processes that are deadlocked.
3
Write a program to implement the deadlock detection algorithm with multiple resources of each type. Your program should read from a file the following inputs: the number of processes, the number of resource types, the number of resources of each type in existence ... a deadlock in the system. In case there is, the program should print out the identities of all processes that are deadlocked.
4
Program a simulation of the banker’s algorithm. Your program should cycle through each of the bank clients asking for a request and evaluating whether it is safe or unsafe. Output a log of requests and decisions to a file.
5
Repeat the previous problem, but now avoid starvation. When a baboon that wants to cross to the east arrives at the rope and finds baboons crossing to the west, he waits until the rope is empty, but no more westward-moving baboons are allowed to start until at least one baboon has crossed the other way.
6
A student majoring in anthropology and minoring in computer science has embarked on a research project to see if African baboons can be taught about deadlocks. He locates a deep canyon and fastens a rope across it, so the baboons can cross hand-overhand ... semaphores that avoids deadlock. Do not worry about a series of eastward-moving baboons holding up the westward-moving baboons indefinitely.
7
Cinderella and the Prince are getting divorced. To divide their property, they have agreed on the following algorithm. Every morning, each one may send a letter to the other's lawyer requesting one item of property. Since it takes a day for letters to ... When they come back from vacation, the computers are still negotiating. Why? Is deadlock possible? Is starvation possible? Discuss your answer.
8
A program contains an error in the order of cooperation and competition mechanisms, resulting in a consumer process locking a mutex (mutual exclusion semaphore) before it blocks on an empty buffer. The producer process blocks on the mutex before it can place a ... waiting for a signal from the producer. Is this a resource deadlock or a communication deadlock? Suggest methods for its control.
9
Local Area Networks utilize a media access method called CSMA/CD, in which stations sharing a bus can sense the medium and detect transmissions as well as collisions. In the Ethernet protocol, stations requesting the shared channel do not transmit frames if they sense ... this a resource deadlock or a livelock? Can you suggest a solution to this anomaly? Can starvation occur with this scenario?
10
Assume two processes are issuing a seek command to reposition the mechanism to access the disk and enable a read command. Each process is interrupted before executing its read, and discovers that the other has moved the disk arm. Each then reissues the seek ... . This sequence continually repeats. Is this a resource deadlock or a livelock? What methods would you recommend to handle the anomaly?
11
Explain the differences between deadlock, livelock, and starvation.
12
Main memory units are preempted in swapping and virtual memory systems. The processor is preempted in time-sharing environments. Do you think that these preemption methods were developed to handle resource deadlock or for other purposes? How high is their overhead?
13
A computer science student assigned to work on deadlocks thinks of the following brilliant way to eliminate deadlocks. When a process requests a resource, it specifies a time limit. If the process blocks because the resource is not available, a timer is started. If the ... the process is released and allowed to run again. If you were the professor, what grade would you give this proposal and why?
14
One way to prevent deadlocks is to eliminate the hold-and-wait condition. In the text it was proposed that before asking for a new resource, a process must first release whatever resources it already holds (assuming that is possible). However, doing so introduces ... that it may get the new resource but lose some of the existing ones to competing processes. Propose an improvement to this scheme.
15
In an electronic funds transfer system, there are hundreds of identical processes that work as follows. Each process reads an input line specifying an amount of money, the account to be credited, and the account to be debited. Then it locks both accounts and transfers ... . (In other words, solutions that lock one account and then release it immediately if the other is locked are not allowed.)
16
A distributed system using mailboxes has two $IPC$ primitives, send and receive. The latter primitive specifies a process to receive from and blocks if no message from that process is available, even though messages may be waiting from other processes. There are no shared resources, but processes need to communicate frequently about other matters. Is deadlock possible? Discuss.
17
Two processes, $A$ and $B,$ each need three records, $1, 2,$ and $3,$ in a database. If $A$ asks for them in the order $1, 2, 3,$ and $B$ asks for them in the same order, deadlock is not possible. However, if $B$ asks for them ... resources, there are $3!$ or six possible combinations in which each process can request them. What fraction of all the combinations is guaranteed to be deadlock free?
18
One way to eliminate circular wait is to have rule saying that a process is entitled only to a single resource at any moment. Give an example to show that this restriction is unacceptable in many cases.
19
A system has four processes and five allocatable resources. The current allocation and maximum needs are as follows: What is the smallest value of x for which this is a safe state?
20
The banker’s algorithm is being run in a system with $m$ resource classes and $n$ processes. In the limit of large $m$ and $n,$ the number of operations that must be performed to check a state for safety is proportional to $m^{a} n^{b}.$ What are the values of $a$ and $b?$
21
Suppose that process $A$ in Fig. 6-12 requests the last tape drive. Does this action lead to a deadlock?
22
Consider the previous problem again, but now with $p$ processes each needing a maximum of $m$ resources and a total of $r$ resources available. What condition must hold to make the system deadlock free?
23
A system has two processes and three identical resources. Each process needs a maximum of two resources. Is deadlock possible? Explain your answer.
24
Take a careful look at Fig. 6-11(b). If $D$ asks for one more unit, does this lead to a safe state or an unsafe one? What if the request came from $C$ instead of $D?$
1 vote
25
Can a system be in a state that is neither deadlocked nor safe? If so, give an example. If not, prove that all states are either deadlocked or safe.
26
In theory, resource trajectory graphs could be used to avoid deadlocks. By clever scheduling, the operating system could avoid unsafe regions. Is there a practical way of actually doing this?
27
Can the resource trajectory scheme of Fig. 6-8 also be used to illustrate the problem of deadlocks with three processes and three resources? If so, how can this be done? If not, why not?
Suppose that in Fig. 6-6 $C_{ij} + R_{ij} > E_{j}$ for some i. What implications does this have for the system?