Os Deadlocks

Topics: Deadlock, Need, AirTrain Newark Pages: 3 (450 words) Published: March 10, 2011
Operating System Sixth Assignment

A) Resource Deadlocks:-

Allocated Maximum Available A B C A B C A B C P1 1 2 3 3 2 6 0 3 1 P2 1 2 0 1 4 2 P3 1 1 1 1 4 2 P4 1 0 2 4 2 2
Compute the Need Matrix. Is the system safe? If so, show the order in which all processes can complete. If the system is not safe, explain.

Ans:-

Need Matrix=Maximum-Allocated

Allocated Maximum Available Needed A B C A B C A B C A B C P1 1 2 3 4 2 6 1 3 1 3 0 3 P2 1 2 0 2 5 3 1 3 3 P3 1 1 1 2 5 2 1 4 1 P4 1 0 2 5 2 3 4 2 1

The system is not safe.Need matrix process needs more resources than avialable matrix.

B )Apply the deadlock detection...
Continue Reading

Please join StudyMode to read the full document

You May Also Find These Documents Helpful

  • Deadlock Essay

    ...deadlock A condition that occurs when two processes are each waiting for the other to complete before proceeding. The result is that both processes hang. Deadlocks occur most commonly in multitasking and client/server environments. Ideally, the programs that are deadlocked, or the operating system, should resolve the deadlock, but this doesn't always happen. A deadlock is also called a deadly embrace. The cause of deadlocks: Each process needing what another process has. This results from sharing resources such as memory, devices, links. In an operating system, a deadlock is a situation which occurs when a process or thread enters a waiting state because a resource requested by it is being held by another waiting process, which in turn is waiting for another resource. If a process is unable to change its state indefinitely because the resources requested by it are being used by another waiting process, then the system is said to be in a deadlock. Prevention Deadlock prevention works by preventing one of the four Coffman conditions from occurring. *Removing the mutual exclusion condition means that no process will have exclusive access to a resource. This proves impossible for resources that cannot be spooled. But even with spooled resources, deadlock could still occur. Algorithms that avoid mutual exclusion are called non-blocking...

    Read More
    779 Words 4 Pages
  • Deadlock Research Paper

    ...Deadlock occurs when each process in a set is waiting for an event that can only be caused by some other process in that set. Basically, deadlock is an operating system issue that reared its head with the advent of multiprogramming environments. First and foremost, a deadlock cannot occur unless there are at least two processes trying to run concurrently. There are actually four distinct circumstances that must be met for deadlock to occur, which will be discussed shortly, but it is worth noting that it is fundamentally a multiprocessing problem. Mono-processing systems do not have to worry about deadlock. The reason is that deadlock involves resource allocation, and if there is only one process, it has uncontested access to all resources. Only certain types of resources are associated with deadlock, and they are of the exclusive-use, non-preemptible type. That is to say, only one process can use the resource at any given time, and once allocated the resource cannot be unallocated by the operating system, but rather the process has control over the resource until it completes its task. Excellent examples of such resources are printers, plotters, tape drives, etc.. Resources that do not fit the criteria are memory and the CPU. While it is convenient to discuss deadlock in terms of hardware resources, there are software resources that are equally good candidates...

    Read More
    1203 Words 5 Pages
  • Deadlock and Deadlocks General Strategies Essay

    ...OPERATING SYSTEMS DEADLOCKS Jerry Breecher 7: Deadlocks 1 OPERATING SYSTEM Deadlocks What Is In This Chapter? • What is a deadlock? • Staying Safe: Preventing and Avoiding Deadlocks • Living Dangerously: Let the deadlock happen, then detect it and recover from it. 7: Deadlocks 2 DEADLOCKS EXAMPLES: • • "It takes money to make money". You can't get a job without experience; you can't get experience without a job. BACKGROUND: The cause of deadlocks: Each process needing what another process has. This results from sharing resources such as memory, devices, links. Under normal operation, a resource allocations proceed like this:: 1. 2. 3. Request a resource (suspend until available if necessary ). Use the resource. Release the resource. 7: Deadlocks 3 DEADLOCKS Bridge Crossing Example • • • • • Traffic only in one direction. Each section of a bridge can be viewed as a resource. If a deadlock occurs, it can be resolved if one car backs up (preempt resources and rollback). Several cars may have to be backed up if a deadlock occurs. Starvation is possible. 7: Deadlocks 4 DEADLOCKS DEADLOCK CHARACTERISATION NECESSARY CONDITIONS ALL of these four must happen simultaneously for a deadlock...

    Read More
    1034 Words 5 Pages
  • Essay about Deadlocks-Resource Allocation Graph

    ...Operating Systems 3 – Deadlocks Lab notes Course lectured by Prof. Gabriel Kuper Lab assist. Ilya Zaihrayeu http://www.dit.unitn.it/~ilya/os.htm Deadlock Prerequisites Deadlock can arise if four conditions hold simultaneously: Mutual exclusion: only one process at a time can use a resource. If another process requests that resource, the requesting process is delayed until the resource is released; Hold and wait: a process holding at least one resource is waiting to acquire additional resources held by other processes; No preemption: a resource can be released only voluntarily by the process holding it, after that process has completed its task; Circular wait: there exists a set {P0, P1, …, Pn} of waiting processes such that P0 is waiting for a resource that is held by P1, P1 is waiting for a resource that is held by P2, …, Pn–1 is waiting for a resource that is held by Pn, and Pn is waiting for a resource that is held by P0 Ilya Zaihrayeu Operating Systems Course 2 Deadlock Prevention Mutual Exclusion not required for sharable resources; for non-sharable resources generally not possible to prevent deadlocks by denying the mutual-exclusion condition a possible solution – a spooler Hold and Wait Require process to request and be allocated all its resources before it begins execution, or allow process to request resources only when the process has none No Preemption If a process that is...

    Read More
    1184 Words 5 Pages
  • Term paper about deadlock

    ... Abstract Operating system is a collection of software that manages computer hardware resources and provides common services for computer programs. In this term paper a thorough discussion of the drawbacks of, and the problems involved in, previous proposals to handle deadlocks in Operating system is provided. A deadlock is a situation which occurs when a process or thread enters a waiting state because a resource requested is being held by another waiting process, which in turn is waiting for another resource. If a process is unable to change its state indefinitely because the resources requested by it are being used by another waiting process, then the system is said to be in a deadlock. In a transaction database, a deadlock happens when two processes each within its own transaction updates two of information but in the opposite order. Several highlights of our proposals are emphasized. Introduction In Operating system, a deadlock is a situation in which two computer programs sharing the same resources are effectively preventing each other from accessing the resource, resulting in both programs ceasing to function. The earliest computer operating system ran only one program at a time. All the resources of the system were available to this one...

    Read More
    1423 Words 6 Pages
  • Essay on Deadlock

    ... Deadlock Jack Pressler POS/355 11-25-2013 Liane Monaco Deadlock Deadlock can occur when the permanent blocking of a set of processes compete for the same system resources. A set of processes is deadlocked when each process in the set is blocked awaiting an event that can only be triggered by another blocked process in the set. Deadlock is permanent because none of the events are ever triggered. Three conditions must take place for a deadlock to take place. The first one is Mutual exclusion, which is a single process that uses one resource at a time. No process may access a resource unit that is being utilized by another process. Hold and wait is the second condition, it can be described as one process that holds assigned resources while waiting for another assignment. Finally, No preemption occurs when no resource can be forced or removed from a process holding it. These three conditions are necessary for a deadlock to exist. However, a fourth condition is required for an actual deadlock to take place. Circular wait occurs when a closed chain of processes exists, and each process holds one or more resources needed by the next process in the chain. This condition is an immediate result of the first three. Below is a self-explanatory illustration of Deadlock. Deadlock blocks a set of processes that competes for system...

    Read More
    426 Words 2 Pages
  • Essay on Impact of Currant Political Deadlock on Pakistan’s Economy, Seminar on Monday

    ...Impact of Currant Political Deadlock on Pakistan’s Economy, Seminar on Monday Islamabad: (Thursday, January 19, 2012) The current political impasse between various state institutions is now costing the macro-economy of Pakistan in the form of stagnant growth and investment. Several structural issues require government’s immediate attention which includes power and gas sector crises, unsustainable losses of public sector enterprises, rising levels of debt burden and slow progress on tax reforms. Due to lack of forward-looking road map government has been unable to build upon and leverage the rising levels of exports which have primarily ridden on deteriorating levels of Pakistani rupee and rising global prices of Pakistani exports in the previous quarter. The balance of payments may soon come under greater pressure as the time for repayment of IMF dues nears. This poor macroeconomic milieu has now implied additional burdens on the poor segment of the population. This segment has been particularly hurt by electricity and gas stoppages in the industry, household and transport sectors. The lack of service delivery not only in infrastructure but also in social sectors such as health has implied a reduced quality of life. Going forward it seems that the government will face some key economic threats which include: rising debt burden, pick up in global oil prices, reduction in exports (due to continued energy constraints) and a further free fall in...

    Read More
    339 Words 2 Pages
  • Deadlock and Exclusive Lock Essay

    ...Assignment 5.1 Instructions: Please submit the answers to the following questions in a Microsoft Word document. This assignment verifies that you understand how shared and exclusive locks work. Suppose that S1, S2, and S3 are sessions connected concurrently to the same database instance. Suppose further that D1, D2, and D3 are data objects that can be locked with a shared and exclusive lock. For the ten locking situations below, indicate, for each session, whether it procures the requested lock, waits, or deadlocks. 1. S1 has a shared lock on D1 and S2 attempts to procure a shared lock on D1. S2 can procure a shared lock on D1 2. S1 has an exclusive lock on D1 and S2 attempts to procure a shared lock on D1. S2 has to wait until S1 releases exclusive lock on D1 3. S1 has a shared lock on D1 and S2 attempts to procure an exclusive lock on D1. S2 must wait until S1 commits in order to procure an exclusive lock on D1 4. S1 has an exclusive lock on D1 and S2 attempts to procure an exclusive lock on D1. S2 must wait to begin until S1 commits in order to procure an exclusive lock on D1 5. S1 has a shared lock on D1, S2 has a shared lock on D1, and S3 attempts to procure a shared lock on D1. S3 can procure a shared lock on D1. 6. S1 has an exclusive lock on D1 and a shared lock on D2, and S2 attempts to procure an exclusive lock on D2. S2 must wait until S1 unlocks D2 in order to procure an exclusive lock...

    Read More
    440 Words 2 Pages

Popular Essays

Become a StudyMode Member

Sign Up - It's Free