dead lock in operating system Presentation1.pptx

Presentation1.pptx

1. Deadlock A  deadlock  is a situation where a set of processes are blocked because each process is holding a resource and waiting for another resource acquired by some other process. 

2.   For example, in the below diagram, Process 1 is holding Resource 1 and waiting for resource 2 which is acquired by process 2, and process 2 is waiting for resource 1. 

3. Normal Resource Allocation Operation Each process utilizes a resource as follows: 1. Request a resource: if request not granted, then process should wait to acquire. 2. Use the resource: process can operate on the resources. 3. Release the resource: the process releases the resources

4. Importance of Understanding Deadlock: Crucial for System Designers, Programmers, and Administrators: Deadlock is a fundamental concept in operating systems that directly impacts system behavior and performance. System designers need to consider deadlock when designing system architectures to ensure reliability and efficiency. Programmers must write code that avoids deadlock situations to prevent system failures and improve application performance. Administrators are responsible for managing system resources and implementing strategies to detect, prevent, or resolve deadlock scenarios. Fundamental Concept in Operating Systems: Deadlock is one of the core concepts in operating systems theory and is studied extensively in computer science. Understanding deadlock helps developers and administrators comprehend the behavior of complex systems and troubleshoot issues effectively.

5. Serious Implications if Not Properly Managed: Deadlock can lead to system crashes, resource starvation, and decreased system throughput. If deadlock is not properly managed, it can severely impact system reliability and user experience. Designing Robust and Reliable Systems: Knowledge of deadlock allows developers to design systems with built-in mechanisms to prevent or handle deadlock situations. By considering deadlock during the design phase, developers can create more robust and reliable software systems. Implementing Effective Strategies: Administrators can implement strategies such as deadlock detection, prevention, and avoidance to mitigate the risk of deadlock in operating systems. Effective management of deadlock helps maintain system stability and ensures smooth operation.

6. Impact on System Performance: Decreased Throughput: Deadlock causes resources to be tied up, halting the progress of affected processes. This leads to decreased overall system throughput as resources are not utilized efficiently. Increased Response Times: Processes waiting for resources in a deadlock experience delays in execution. As a result, system response times increase, leading to slower performance for users or applications. Risk of System Crashes: In extreme cases, deadlock can escalate to system crashes or freezes. When deadlock persists, the system may become unresponsive, requiring manual intervention to recover. Inefficient Resource Utilization: Resources remain idle or are locked by processes involved in a deadlock. This inefficient use of resources reduces system efficiency and can impact overall system performance. Essential for System Stability: Managing deadlock is crucial for maintaining system stability and preventing disruptions in operation. Implementing strategies to detect, prevent, or resolve deadlock situations helps ensure smooth and reliable system performance.

7. conditions for Deadlock  Deadlock can arise if four conditions hold simultaneously 1. Mutual exclusion:  In this condition, only one method must be non-shareable. It means only one process can use it at a time. This condition ensures that a resource cannot be simultaneously accessed or modified by multiple processes.  2. Hold and wait : The process must hold at least one resource while waiting to acquire additional resources. This condition can lead to a situation where processes hold some resources and wait indefinitely for others.   3. Preemption and non-preemption : Preemption is act of taking a resource from a process before it has finished its task. No pre-emption :  A resource cannot be taken from a process unless the process releases the resource 4. Circular wait : there exists a set {P0, P1, …, P0} 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 P0 is waiting for a resource that is held by P0.

8. Resource Allocation Graph An arrow from the process to resource indicates the process is requesting the resource. An arrow from resource to process shows an instance of the resource has been allocated to the process. Process is a circle, resource type is square; dots represent number of instances of resource in type. Request points to square, assignment comes from dot. source has been allocated to the process. Process Resource P R

9. If the graph contains no cycles, then no process is deadlocked. If there is a cycle, then: ➢If resource types have multiple instances per resource type, then possibility of deadlock MAY exist. ➢If each resource type has one instance per resource type, then deadlock has occurred. P1 P2 R2 R1