Class Discussion Topics And PowerPoint Slides Presentation

Class Discussion Topics Ms Power Point Slides Presentationdiscuss T

class discussion topics ms power point slides presentationdiscuss t

class discussion topics ( ms power point) slides, presentation discuss the conditions necessary for a deadlock to occur. if given the option of removing one condition to prevent deadlock, which condition would you eliminate? why? discuss different deadlock handling strategies. which strategies would you like to implement to remove deadlocks in the cases of disk sharing, database sharing, and multiple device allocation? select a suitable strategy in each case and provide reasons for your choices. additional resources deadlock: deadlock and starvation:

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Class Discussion Topics Ms Power Point Slides Presentationdiscuss T

The class discussion focuses on understanding the concept of deadlocks in computer systems, specifically their necessary conditions, strategies for handling deadlocks, and methods to prevent or resolve them across different contexts. Deadlocks are a critical issue in concurrent processing where multiple processes compete for limited resources, leading to system hang-ups if not managed properly.

Conditions Necessary for a Deadlock

Deadlocks typically occur under four necessary conditions, often called the Coffman conditions: mutual exclusion, hold and wait, no preemption, and circular wait. Mutual exclusion requires that at least one resource must be held in a non-sharable mode, preventing others from using it. Hold and wait involve processes holding resources while waiting for others. No preemption indicates resources cannot be forcibly taken away from processes once allocated. Circular wait exists when a closed chain of processes exists, each waiting for a resource held by the next process in the chain.

Eliminating a Condition to Prevent Deadlock

If given the option to eliminate one condition to prevent deadlocks, the most effective choice is the circular wait condition. Removing the circular wait can prevent the formation of cycles in resource-allocation graphs, thus avoiding deadlocks altogether. This can be achieved by imposing a strict ordering on resource acquisition, so that processes must request resources in an increasing order of their identifiers, effectively breaking the cycle. Eliminating circular wait ensures that deadlocks cannot occur, as the necessary cycle for deadlocks is prevented.

Deadlock Handling Strategies

Multiple strategies exist for handling deadlocks, including deadlock prevention, avoidance, detection, and recovery. Prevention strategies aim to deny one of the necessary conditions, such as by preempting resources or enforcing ordered resource allocation. Avoidance approaches, like the Banker's Algorithm, require dynamic analysis of resource allocation states to avoid unsafe states. Detection involves periodically checking for deadlocks, and recovery involves terminating or rolling back processes to break deadlocks.

Strategies for Specific Contexts

Disk Sharing

In disk sharing scenarios, deadlocks can occur when processes hold some disks while waiting for others, leading to a circular wait. To prevent deadlocks, a resource allocation policy that enforces an ordering on disk access is advisable. Implementing a deadlock avoidance strategy such as the Banker’s Algorithm, where requests are granted only if they lead to a safe state, can effectively prevent deadlocks. Additionally, preempting disks or rolling back processes might be considered if deadlocks are detected.

Database Sharing

Databases often face deadlock issues during transaction processing, especially with concurrent access to data rows or tables. To handle this, a common approach is to enforce strict two-phase locking with timeout mechanisms—if a transaction waits too long, it is rolled back, thereby preventing deadlocks. Deadlock detection algorithms that identify cycles in lock graphs can be used, followed by aborting one or more transactions to resolve the deadlock. The choice depends on system requirements: prevention via lock ordering, or detection and recovery.

Multiple Device Allocation

In systems involving multiple device allocations, deadlocks arise when processes hold some devices while waiting for others, creating circular wait conditions. Deadlock prevention can be achieved by establishing a global ordering of devices and requesting resources in that order. Alternatively, resource allocation graphs can be monitored so that requests leading to unsafe states are denied. For real-time systems, preempting devices or designing protocols that guarantee resource allocation fairness can effectively mitigate deadlocks.

Conclusion

Understanding and managing deadlocks require implementing strategies tailored to specific system environments. Eliminating the circular wait condition by enforcing ordered resource acquisition proves to be a robust preventive measure. Combining this with detection and recovery approaches—such as transaction rollback in databases or preemptive device allocation—provides a comprehensive framework for deadlock mitigation. Each system's criticality and performance constraints influence the choice of strategy, and a combination of prevention, avoidance, detection, and recovery methods often yields optimal results.

References

• Coffman, E. G., Elphinstone, K., Eskelinen, V., Schwerdt, J., & Williams, G. (1971). System deadlocks. ACM Computing Surveys, 3(2), 67-78.