Deadlocks Demystified in Multi-Core Systems Quiz

Explore the key concepts and mechanisms behind deadlocks in multi-core systems with this quiz, designed to enhance your understanding of resource allocation, detection, and prevention techniques. Sharpen your knowledge of deadlock conditions and resolution strategies crucial for efficient multi-core computing.

1. Basic Deadlock Concept

   Which situation best illustrates a deadlock in a multi-core system?

   1. All processes share resources without any delays.
   2. Two processes each hold one resource and wait for the other’s resource indefinitely.
   3. Processes run independently on separate cores and finish at different times.
   4. A single process completes rapidly without waiting.

   Explanation: A deadlock occurs when two or more processes hold resources and wait indefinitely for resources held by the other, preventing progress. The other options describe cases where processes do not block each other or are not waiting for held resources. 'Processes run independently' and 'completes rapidly' do not involve circular resource waiting, while 'share resources without delays' indicates no contention.

2. Necessary Deadlock Condition

   Which condition is necessary for a deadlock to occur in a multi-core system?

   1. Mutual exclusion
   2. Unlimited resources
   3. Preemption always possible
   4. No resource contention

   Explanation: Mutual exclusion means that at least one resource cannot be shared and only one process can use it at a time, which is a required condition for deadlock. The other options, like preemption always being possible and unlimited resources, eliminate deadlocks. 'No resource contention' also means deadlock can't occur, making 'mutual exclusion' the correct answer.

3. Hold and Wait Example

   In the scenario where Process A holds Resource X and waits for Resource Y, which deadlock condition is being fulfilled?

   1. Circular waiting
   2. Preemption
   3. Hold and wait
   4. Resource transition

   Explanation: Hold and wait occurs when a process holds at least one resource and waits to acquire additional ones, as in the scenario described. Circular waiting involves more than two processes waiting for each other's resources, which is not shown here. Preemption relates to forcibly taking resources, which isn't the case, and 'resource transition' is not a standard deadlock term.

4. Deadlock Prevention

   What is an effective method to prevent deadlocks in multi-core systems?

   1. Allowing resources to be held indefinitely
   2. Disabling multi-core processing
   3. Using random number allocation
   4. Forcing processes to request all required resources at once

   Explanation: Having processes request all resources at once avoids ‘hold and wait,’ thus preventing one of the necessary deadlock conditions. Allowing indefinite holding increases deadlock risk, disabling multi-core processing is unnecessary and impractical, and random number allocation does not address deadlocks at all.

5. Circular Wait

   What does ‘circular wait’ mean in the context of multi-core system deadlocks?

   1. A process loops rapidly without acquiring resources
   2. Processes alternate between cores in a cycle
   3. Resources are assigned in a round-robin manner
   4. A set of processes each waiting for a resource held by the next process in the circle

   Explanation: Circular wait is when each process in a set is waiting for a resource held by another, forming a cycle that prevents progress. Rapid looping without resources or round-robin assignment doesn't create deadlock. Alternating between cores is unrelated to resource waiting.

6. Resource Allocation Graphs

   How can a resource allocation graph be used to detect potential deadlocks in a multi-core system?

   1. By counting the number of processes
   2. By identifying cycles in the graph structure
   3. By measuring core clock speeds
   4. By monitoring memory usage only

   Explanation: Cycles in a resource allocation graph indicate possible deadlocks since they represent circular waiting. Counting processes, measuring clock speeds, or monitoring memory does not detect deadlocks directly. Resource allocation graphs specifically help visualize and analyze resource dependencies.

7. Deadlock Resolution

   If a deadlock is detected in a multi-core system, which action can help resolve it?

   1. Ignoring the issue and waiting
   2. Terminating one or more involved processes
   3. Reducing CPU frequency
   4. Increasing the number of processor cores

   Explanation: Terminating processes involved in a deadlock releases their resources, breaking the cycle and resolving the deadlock. Adding more cores or reducing frequency does not resolve resource cycles. Ignoring the issue won't help, as the processes will remain stuck indefinitely.

8. Starvation vs Deadlock

   What is the main difference between starvation and deadlock in multi-core systems?

   1. In deadlock, all involved processes are stuck forever; in starvation, processes wait indefinitely but are not necessarily blocked by others.
   2. Deadlock involves memory read errors, while starvation is about CPU overheating.
   3. Deadlock always resolves itself, starvation never does.
   4. Starvation only happens on single-core systems.

   Explanation: In deadlock, processes form a cycle and are permanently blocked, while in starvation a process might continually wait due to resource scheduling but not from a circular block. 'Deadlock always resolves itself' is false. Starvation can occur on multi-core systems too, and neither is related to hardware errors or overheating.

9. Deadlock Avoidance Algorithm

   Which algorithm is used to avoid deadlocks in resource allocations for multi-core systems?

   1. Round Robin
   2. Bubble Sort
   3. Fisher-Yates algorithm
   4. Banker’s algorithm

   Explanation: Banker’s algorithm checks resource allocation safety to avoid deadlocks by granting only safe requests. Fisher-Yates is for shuffling, Bubble Sort is a sorting algorithm, and Round Robin is a process scheduling method, none of which address deadlock prevention.

10. Real-world Scenario

    In a multi-core system where Process 1 has locked Printer and is waiting for Disk, while Process 2 has locked Disk and is waiting for Printer, what has occurred?

    1. Parallel execution is maximized
    2. A deadlock has happened due to circular waiting
    3. A process priority conflict
    4. Resource contention without deadlock

    Explanation: This scenario describes both hold-and-wait and circular waiting, causing deadlock. While there is resource contention, the mutual waiting explains deadlock specifically. Parallel execution is not maximized, and no priority issue is described.