Deadlock in network operating system pdf

Phrasemes in Language and Phraseology in Linguistics. Verification of the Gross Mass of a Packed Container. Jump to Page. Search inside document. Never block an intersection Must back up if you find yourself doing so Why does this work? Reactive Approaches: Periodically check for evidence of deadlock For example, using a graph reduction algorithm Then need a way to recover Could blue screen and reboot the computer Could pick a victim and terminate that thread But this is only possible in certain kinds of applications Basically, thread needs a way to clean up if it gets terminated and has to exit in a hurry!

Proactive Approaches: Deadlock Prevention Prevent one of the 4 necessary conditions from arising. This will prevent deadlock from occurring Deadlock Avoidance Carefully allocate resources based on future knowledge Deadlocks are prevented 3. Ignore the problem Pretend deadlocks will never occur Ostrich approach but surprisingly common! Thank you For Listening. Chloe Zha. Chemtrails Equals Treason. Binod Lungelee.

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Basically in the Normal mode of Operation utilization of resources by a process is in the following sequence:. Request: Firstly, the process requests the resource. In a case, if the request cannot be granted immediately e. Use: The Process can operate on the resource e. According to this condition, atleast one resource should be non-shareable non-shareable resources are those that can be used by one process at a time. According to this condition, A process is holding atleast one resource and is waiting for additional resources.

Resources cannot be taken from the process because resources can be released only voluntarily by the process holding them. The above four conditions are not completely independent as the circular wait condition implies the hold and wait condition.

We emphasize on the fact that all four conditions must hold for a deadlock. Deadlock conditions can be avoided with the help of a number of methods. Let us take a look at some of the methods. According to this method, it is assumed that deadlock would never occur. This approach is used by many operating systems where they assume that deadlock will never occur which means operating systems simply ignores the deadlock.

This approach can be beneficial for those systems that are only used for browsing and for normal tasks. Thus ignoring the deadlock method can be useful in many cases but it is not perfect in order to remove the deadlock from the operating system.

As we have discussed in the above section, that all four conditions: Mutual Exclusion, Hold and Wait, No preemption, and circular wait if held by a system then causes deadlock to occur. The main aim of the deadlock prevention method is to violate any one condition among the four; because if any of one condition is violated then the problem of deadlock will never occur.

As the idea behind this method is simple but the difficulty can occur during the physical implementation of this method in the system. This method is used by the operating system in order to check whether the system is in a safe state or in an unsafe state.

This method checks every step performed by the operating system. Any process continues its execution until the system is in a safe state. Once the system enters into an unsafe state, the operating system has to take a step back. Disks tend to represent a major bottleneck in system performance, since they are the slowest main computer component.

In this section, we discuss a variety of techniques used to improve the efficiency and performance of secondary storage. Ans: Recovery Files and directories are kept both in main memory and on disk, and care must taken to ensure that system failure does not result in loss of data or in data inconsistency.

Ans: Log-Structured File Systems Computer scientists often find that algorithms and technologies originally used in one area are equally useful in other areas. Such is the case with the database log-based recovery algorithms described in Section 6.

These logging algorithms have been applied successfully to the problem of consistency checking. The resulting implementations are known as log-based transaction-oriented or journaling file systems.

As a result, file-system design and implementation command quite a lot of attention from system designers. Others are optimized for specific tasks in an attempt to provide better performance in those areas than general-purpose file systems. The main difference between the two is the way in which they are geographically distributed. Local-area networks are composed of processors distributed over small areas such as a single building?

These differences imply major variations in the speed and reliability of the communications network, and they are reflected in the distributed operating-system design. Ans: Network Topology The sites in a distributed system can be connected physically in a variety of ways. Each configuration has advantages and disadvantages. The cost in time and money to send a message from site A to site B The extent to which data can be accessed despite the failure of some links or sites view more..

Ans: Revocation of Access Rights In a dynamic protection system, we may sometimes need to revoke access rights to objects shared by different users view more.. Ans: We survey two capability-based protection systems. These systems vary in their complexity and in the types of policies that can be implemented on them.

Neither system is widely used, but they are interesting proving grounds for protection theories view more.. Ans: Robustness A distributed system may suffer from various types of hardware failure. The failure of a link, the failure of a site, and the loss of a message are the most common types. To ensure that the system is robust, we must detect any of these failures, reconfigure the system so that computation can continue, and recover when a site or a link is repaired. Previous Page.

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