Understanding Deadlocks: Detection, Prevention, and Recovery Quiz Quiz

Explore core concepts of deadlocks, including their conditions, detection techniques, prevention strategies, and recovery methods in concurrent systems. This quiz provides clear questions to help you reinforce your understanding of deadlock challenges and solutions.

1. Deadlock Definition

   Which of the following best describes a deadlock in operating systems?

   1. A system error caused by missing resource allocation.
   2. A situation where two or more processes are unable to proceed because each is waiting for the other to release a resource.
   3. A state where a process completes execution without using all its resources.
   4. A scenario where all processes are running but none is making progress due to high CPU usage.

   Explanation: A deadlock occurs when processes become stuck, each waiting for resources held by the other. The other options are incorrect: a process not using all resources doesn't cause deadlock, high CPU usage can stall progress but is not a deadlock, and a system error from missing resource allocation is unrelated to deadlocks.

2. Coffman Conditions

   Which one of the following is NOT one of the four Coffman conditions necessary for deadlock?

   1. Mutual exclusion
   2. Spooling
   3. Hold and wait
   4. Circular wait

   Explanation: Spooling is not a Coffman condition; it's a technique for handling data streams. The four Coffman conditions for deadlock are mutual exclusion, hold and wait, no preemption, and circular wait. The options mutual exclusion, circular wait, and hold and wait are all correct Coffman conditions.

3. Circular Wait Example

   If process A waits for a resource held by B, B waits for a resource held by C, and C waits for a resource held by A, which deadlock condition does this illustrate?

   1. No preemption
   2. Circular wait
   3. Mutual iteration
   4. Exclusive access

   Explanation: This scenario shows a cycle of processes each waiting for another, which is the circular wait condition. No preemption refers to inability to forcibly take resources back. Mutual iteration is not a deadlock term. Exclusive access resembles mutual exclusion, but that's not the condition depicted here.

4. Deadlock Detection

   What data structure is commonly used by deadlock detection algorithms to identify cycles representing deadlocks?

   1. Stack trace
   2. Resource allocation graph
   3. Hash table
   4. Priority queue

   Explanation: Resource allocation graphs map out processes and resources, allowing detection algorithms to spot cycles that indicate deadlocks. Priority queues and hash tables serve different purposes in resource management and searching. Stack traces are used for debugging, not specifically for deadlock detection.

5. Deadlock Prevention Strategy

   Which strategy can help prevent deadlocks by making sure that all resources a process will need are allocated to it at once?

   1. Allow circular wait
   2. Ignore resource needs
   3. Request all resources upfront
   4. Grant partial allocation

   Explanation: Ensuring a process requests all required resources up front eliminates hold and wait, thus preventing deadlock. Allowing circular wait is a cause, not a solution. Partial allocation permits hold and wait, which is risky. Ignoring resource needs does not prevent deadlocks and may worsen resource management.

6. Safe State Recognition

   When using the Banker's algorithm, what is considered a 'safe state'?

   1. A state where system resources are over-allocated
   2. A state where only one process holds all resources
   3. A state where processes can complete without entering deadlock
   4. A state where no process can run

   Explanation: A safe state means resources can be allocated such that all processes finish without any deadlock. Over-allocation is unsafe, and no process running isn't related to safety. A single process holding all resources doesn't guarantee overall system safety.

7. Deadlock Recovery Method

   If a deadlock is detected, which action is a common recovery technique?

   1. Continue running all processes
   2. Reschedule all running processes
   3. Abort one or more involved processes
   4. Improve network bandwidth

   Explanation: Killing or aborting affected processes can break a deadlock and restore normal operations. Continuing all processes keeps the system in deadlock. Rescheduling doesn't always resolve the cycle. Network bandwidth is unrelated to deadlock management.

8. No Preemption Condition

   What does the 'no preemption' condition mean in the context of deadlocks?

   1. Only one process can access a resource at a time.
   2. System can interrupt processes at any time.
   3. Resources allocated to a process cannot forcibly be taken away until released by that process.
   4. Processes request all resources simultaneously.

   Explanation: 'No preemption' means once given, resources cannot be forcibly removed. Exclusive resource use is the mutual exclusion condition. Requesting all resources at once is a prevention method, not no preemption. The system’s ability to interrupt processes at any time is about scheduling and not specifically about resource preemption.

9. Resource Allocation Protocols

   Which protocol prevents deadlock by ensuring that resources are always allocated in a predefined global order?

   1. Resource hoarding protocol
   2. Resource ordering protocol
   3. First-come, first-served protocol
   4. Randomized access protocol

   Explanation: Resource ordering prevents circular wait by establishing a strict allocation sequence. Randomized access can still result in deadlocks. First-come, first-served does not prevent cycles inherently. 'Resource hoarding protocol' is not a standard term in deadlock prevention.

10. Starvation vs. Deadlock

    How does starvation differ from deadlock in a resource allocation system?

    1. Starvation is another term for deadlock.
    2. Deadlock always resolves itself over time, while starvation does not.
    3. Starvation happens only in single-threaded systems, deadlocks happen only in multithreaded systems.
    4. In starvation, a process may wait indefinitely, but in deadlock, a group of processes are permanently blocked.

    Explanation: With starvation, one or more processes never acquire needed resources, but others may proceed. Deadlock involves a group of processes blocking each other with no progress. Calling starvation another term for deadlock is wrong; they are different concepts. Deadlocks do not resolve themselves automatically, and both issues can happen in various system configurations.