📝 Deadlocks System Model in Operating System (51 MCQs)

📖 From Operating System • 7. Deadlocks • 51 questions available

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What is Deadlocks System Model in Operating System?

Definition:
The system model abstracts the OS as a collection of processes and resource types, defining how resources are requested, allocated, and released through standard operations like request, use, and release.

Example:
A model defines $n$ processes $\{P_1, P_2, ..., P_n\}$ and $m$ resource types $\{R_1, R_2, ..., R_m\}$ where each $R_j$ has $W_j$ instances available for allocation.

Reason:
This abstraction allows designers to mathematically analyze resource interactions and develop general algorithms for deadlock handling without being tied to specific hardware implementations.

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📝 All Deadlocks System Model in Operating System MCQs

Q1. What does a 'resource type' refer to in the context of a deadlock system model?

A.A specific physical device like a CPU or printer.

B.A category of resources with identical instances. ✅

C.The total number of resources available in the system.

D.A single instance of a hardware component.

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: A resource type is a broad category, such as 'printer' or 'CPU'. Each type consists of one or more identical instances. The definition focuses on the class of resources, not a specific device or a single instance, allowing for multiple identical items to be managed collectively.

Q2. If a system has four identical CPUs, how is this represented in a deadlock model?

A.The system has one resource type 'CPU' with four instances. ✅

B.The system has four resource types of 'CPU' each with one instance.

C.The system has one resource type 'CPU' with one instance.

D.The system has no resource types because CPUs are not considered resources.

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: In the system model, resources are partitioned into types. A resource type like 'CPU' can have multiple identical instances. The number of instances represents the count of that resource available in the system. Four identical CPUs are therefore one resource type with four instances.

Q3. Two printers in a system are considered to be in the same resource class under what condition?

A.They are physically located on the same floor.

B.They are the same brand and model.

C.Any instance of the printer type can satisfy a request for a printer. ✅

D.They are connected to the same network.

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: For resources to be in the same class, their instances must be identical from the user's or system's perspective. This means a request for 'a printer' can be satisfied by any available printer in that class. The physical location or brand is irrelevant to the system's resource allocation logic if they are functionally equivalent.

Q4. In a system with two printers, one on the 9th floor and one in the basement, why might they be defined as separate resource classes?

A.The basement printer is slower.

B.Users on the 9th floor do not consider them equivalent. ✅

C.The operating system cannot manage printers on different floors.

D.They have different paper capacities.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: If users on the 9th floor cannot or do not want to use the basement printer, then from their perspective, the printers are not identical. The system must define separate resource classes to reflect this real-world constraint. The request for 'a printer' cannot be satisfied by either; it must be specific to a location, making the instances non-interchangeable.

Q5. Defining resource classes properly is crucial for deadlock modeling. What is the primary risk of improperly defining a resource class?

A.The system will run slower due to inefficient allocation.

B.The system might allocate an unacceptable resource, or fail to model a real-world constraint. ✅

C.The system will consume more memory for the resource table.

D.The system will automatically reboot.

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: If a class is defined too broadly, the system may allocate a resource (like a printer) that is not acceptable to the requesting process (e.g., a printer in a different building). If defined too narrowly, it may fail to model the competition for resources accurately, potentially hiding or causing deadlock conditions. The core issue is misrepresenting the true state and constraints of the system.

Q6. According to the text, mutex locks and semaphores are considered what kind of resources in a system?

A.Physical resources

B.Logical resources ✅

C.Non-sharable resources

D.I/O resources

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The text explicitly categorizes synchronization tools like mutex locks and semaphores as logical resources. Unlike physical resources (printers, CPU cycles), they are software constructs used for synchronization, but they are still subject to the same deadlock principles as physical resources.

Q7. Why is each mutex lock typically assigned its own resource class?

A.To simplify the code for the operating system.

B.Because each lock protects a specific, unique data structure. ✅

C.To prevent processes from using the wrong lock.

D.To reduce the total number of resource types in the system.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: A mutex lock is usually created to protect a specific data structure (e.g., a queue or linked list). Since the data structure it protects is unique, the lock itself must be uniquely identified to manage access correctly. Assigning it its own resource class reflects its unique purpose and the distinct resource it represents in the system.

Q8. If a mutex lock and a semaphore are both used to protect the same critical section, what is the primary consideration for deadlock modeling?

A.They are both logical resources and can be involved in a deadlock. ✅

B.The mutex lock is safer than a semaphore.

C.The semaphore is faster, so it is less likely to cause a deadlock.

D.They cannot be involved in a deadlock because they are software constructs.

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: Both mutex locks and semaphores are logical resources. A deadlock can occur when processes hold one of these resources while waiting for another. The specific type of synchronization tool is less important than the fact that they are resources that can be requested, held, and released, and can thus be part of a circular wait.

Q9. In the context of resource classes, how is a mutex lock that protects a linked list different from a mutex lock that protects a queue?

A.The linked list lock is more efficient.

B.They protect different data structures, so they are distinct resource classes. ✅

C.The queue lock is more prone to deadlocks.

D.They are functionally identical and belong to the same resource class.

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Each lock is designed to protect a specific piece of data. The lock for a linked list ensures exclusive access to that list, and the lock for a queue ensures exclusive access to that queue. They serve different purposes and protect different resources, so they must be considered separate resource classes in the deadlock model.

Q10. A process must request a resource before using it. What is the fundamental reason for this rule?

A.To ensure the operating system can track resource usage. ✅

B.To prevent processes from accessing resources they are not authorized to use.

C.To guarantee that the process has exclusive control of the resource.

D.To maintain a consistent view of resource allocation.

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: While authorization and exclusivity are important, the fundamental reason is for the OS to manage the finite pool of resources effectively. By requiring a request, the OS can maintain a system table, update it, and manage the allocation state. This accounting is essential to prevent conflicts and manage the competing needs of multiple processes, even if it doesn't directly prevent deadlocks.

Q11. In the standard resource utilization sequence, what is the correct order of operations for a process?

A.Release, Request, Use

B.Request, Use, Release ✅

C.Use, Request, Release

D.Request, Release, Use

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The normal mode of operation for a process using a resource follows a strict sequence: it must first request the resource, then use it, and finally release it when it is done. This is a fundamental rule of resource management in operating systems.

Q12. A process requests a printer, uses it to print a document, and then releases it. What is this sequence an example of?

A.The deadlock cycle

B.The standard resource utilization sequence ✅

C.The dining-philosophers problem

D.A system call error

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The text explicitly defines this as the normal mode of operation for a process utilizing a resource. The three steps are: 1. Request, 2. Use, and 3. Release. This is a standard and expected sequence in a well-behaved system.

Q13. What happens if a process's request for a resource cannot be granted immediately?

A.The process is terminated.

B.The process must wait until the resource is available. ✅

C.The process continues without the resource.

D.The operating system ignores the request.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: If a requested resource is currently being used by another process, the request cannot be satisfied. The process has no choice but to enter a waiting state until the resource becomes free and is granted to it. This is a key condition that can lead to a deadlock if the resource is never released.

Q14. Which of the following is NOT a typical system call used for resource management as described in the text?

A.request()

B.open()

C.create() ✅

D.wait()

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: The text explicitly mentions `request()`, `release()`, `open()`, `close()`, `allocate()`, `free()`, `wait()`, and `signal()` as examples of system calls for resource management. `create()` is a system call for creating a process or file, but it is not listed as a direct resource request/release call in this context.

Q15. The `signal()` operation on a semaphore is analogous to which step in the standard resource utilization sequence?

A.Request

B.Use

C.Release ✅

D.Wait

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: The `signal()` operation on a semaphore increments its value, indicating that a resource is now available. This is the logical equivalent of releasing a resource. The `wait()` operation decrements the semaphore, which is analogous to requesting a resource. Therefore, `signal()` corresponds to the 'Release' step in the sequence.

Q16. What is the primary purpose of the system table in the context of resource allocation?

A.To store the code of all running processes.

B.To track which resources are free and which are allocated to which process. ✅

C.To manage the CPU scheduling algorithm.

D.To store user account information.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The system table is the central data structure for resource management. It records the state of every resource in the system, indicating whether it is free or allocated, and if allocated, which process currently holds it. This information is crucial for managing resource requests and detecting potential deadlocks.

Q17. If a process requests a resource that is currently allocated to another process, where is the requesting process often placed?

A.In a queue of processes waiting for that resource. ✅

B.In a terminated state.

C.In a suspended state on disk.

D.In the ready queue for the CPU.

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: When a resource is busy, the requesting process cannot proceed. The OS will typically add it to a queue associated with that specific resource. This waiting queue contains all the processes that are blocked waiting for that particular resource to become available.

Q18. A system table indicates that a specific resource is 'allocated'. What information does it also record?

A.The total number of requests made for the resource.

B.The priority of the process using the resource.

C.The process to which the resource is allocated. ✅

D.The time at which the resource was allocated.

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: The system table not only marks a resource as allocated but also records the owning process. This is essential for tracking who is holding what. If a deadlock occurs, this information is necessary to identify the processes involved and the resources they hold.

Q19. How does the operating system ensure a process is using a kernel-managed resource correctly?

A.It relies on the process's good behavior.

B.It checks that the process has requested and been allocated the resource. ✅

C.It preempts the process and checks its memory for resource usage.

D.It only allows root processes to access resources.

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: For every use of a kernel-managed resource, the OS performs a validation check. It verifies that the process has indeed made a legitimate request for the resource and that the resource has been allocated to it. This prevents a process from using a resource it hasn't properly acquired, which could bypass the system's resource management logic.

Q20. The system table records whether a resource is free or allocated. What is a potential security concern if this table is not properly managed?

A.A process might be able to allocate resources it does not own. ✅

B.The system might run out of memory to store the table.

C.The system might become too slow to respond to resource requests.

D.The table might be corrupted, causing a system crash.

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: If the system table is not correctly maintained, a process might attempt to use a resource it wasn't allocated, or the OS might incorrectly grant a request for a resource that is already allocated. This represents a fundamental failure in resource management, leading to data corruption, race conditions, and severe system instability.

Q21. A set of processes is in a deadlocked state when every process in the set is waiting for an event. What is the key characteristic of this event?

A.It can be caused by the operating system scheduler.

B.It can only be caused by another process in the same set. ✅

C.It is a timer that will eventually expire.

D.It is an external event like a user pressing a key.

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The formal definition of a deadlock centers on this circular dependency. Each process is waiting for an event (like a resource release), and that event can only be triggered by another process in the same waiting set. This creates the unbreakable cycle that defines a deadlock.

Q22. In a deadlock, processes are primarily waiting for which type of event?

A.CPU time slice expiration

B.I/O completion

C.Resource acquisition and release ✅

D.Program termination

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: The text specifies that the events of main concern are resource acquisition and release. A process in a deadlock is waiting for a resource to be released, which is an event that can only be caused by the process holding that resource, creating the circular dependency.

Q23. Can a deadlock involve both physical and logical resources simultaneously?

A.No, a deadlock can only involve one type of resource.

B.Yes, deadlocks can involve any mix of physical and logical resources. ✅

C.No, logical resources cannot cause deadlocks.

D.Yes, but only if the logical resources are semaphores.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The text explicitly states that deadlocks can involve physical resources (printers, tape drives) or logical resources (semaphores, mutex locks, files). It is entirely possible for a deadlock to involve a mix of both, such as a process holding a mutex lock while waiting for a printer.

Q24. Which of the following is an example of a logical resource that can be involved in a deadlock?

A.A printer

B.A CPU cycle

C.A mutex lock ✅

D.A DVD drive

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: Logical resources are abstract concepts like synchronization primitives. A mutex lock is a classic example. It is a system resource that can be requested, held, and released. A process waiting for a mutex lock held by another process is a common source of deadlocks, especially in multithreaded applications.

Q25. The text mentions that events other than resource acquisition and release can cause deadlocks. Which facility from a previous chapter is cited as an example?

A.CPU scheduling algorithms

B.IPC (Inter-Process Communication) facilities ✅

C.Memory management techniques

D.File systems

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The text references the IPC facilities discussed in Chapter 3. Deadlocks can occur when processes are waiting for messages or other communication events that will only be sent by another process in the deadlocked set. This shows that the concept of a circular wait extends beyond just resource allocation.

Q26. In the example with three processes and three CD-RW drives, what triggers the deadlock?

A.All drives are faulty.

B.Each process holds one drive and requests another. ✅

C.The operating system fails to allocate drives correctly.

D.The processes have the same priority.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The deadlock scenario arises when each of the three processes holds one CD-RW drive. When they each subsequently request another drive, a circular wait is formed. Process 1 waits for a drive held by Process 2, Process 2 waits for Process 3, and Process 3 waits for Process 1, resulting in a deadlock.

Q27. A deadlock involving three processes and three CD-RW drives is an example of a deadlock with what characteristic?

A.Different resource types

B.The same resource type ✅

C.Logical resources only

D.A single process

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: This example specifically illustrates a deadlock using the same resource type (CD-RW drives). Each process requests an instance of the same resource type, and the deadlock arises because all instances are held and each process needs one more, creating a cycle of dependency.

Q28. In the scenario with one printer and one DVD drive, what causes the deadlock between processes Pi and Pj?

A.Both processes request the printer simultaneously.

B.Pi holds the DVD and requests the printer, while Pj holds the printer and requests the DVD. ✅

C.The processes are running with low priority.

D.The printer runs out of paper.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: This is a classic example of a deadlock with different resource types. Pi is holding the DVD drive and waiting for the printer. Pj is holding the printer and waiting for the DVD drive. They are caught in a circular wait, each holding a resource the other needs, which is the definition of a deadlock.

Q29. How do the two deadlock examples (three CD-RW drives and printer/DVD drive) differ fundamentally?

A.Only one involves physical resources.

B.Only one can be resolved by the operating system.

C.One involves a single resource type, while the other involves two different types. ✅

D.One is more common than the other.

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: The fundamental difference lies in the resource types involved. The CD-RW example shows a deadlock can occur with a single resource type (three identical drives). The printer/DVD example demonstrates that a deadlock can also involve two or more different resource types, creating a more complex cycle of dependencies.

Q30. In the CD-RW drive example, each process is waiting for an event 'CD-RW is released.' Why is this event never going to happen?

A.The processes are not programmed to release resources.

B.The release event can only be caused by another waiting process, which is also waiting. ✅

C.The operating system has disabled the release system call.

D.The CD-RW drives are physically broken.

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: This is the core of the deadlock. Process 1 is waiting for a drive to be released, but that release can only occur if Process 2 finishes, which requires a drive, and so on. Since each process is waiting for another, none can proceed to release their own drive, so the required event (release) never occurs.

Q31. What is the significance of the dining-philosophers problem in the context of deadlocks?

A.It provides a solution to all deadlock problems.

B.It illustrates a classic deadlock scenario involving the allocation of multiple resources. ✅

C.It describes how to prevent race conditions.

D.It is a model for CPU scheduling.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The dining-philosophers problem is a well-known thought experiment used to illustrate the complexities of resource allocation and synchronization. It perfectly demonstrates how a simple, seemingly well-behaved set of processes (philosophers) can enter a deadlock if they all acquire resources (chopsticks) in a certain way, highlighting the need for careful lock management.

Q32. Why must developers of multithreaded applications remain aware of deadlocks?

A.To ensure their applications are the fastest.

B.To prevent their applications from getting into a state where they are permanently blocked. ✅

C.To reduce the memory footprint of their applications.

D.To improve the graphical user interface.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: In a multithreaded application, threads share resources. If locks are not managed carefully, a deadlock can cause two or more threads to wait indefinitely for each other's locks. This leads to the entire application or a critical part of it becoming permanently blocked and unresponsive.

Q33. The text states that locking tools are designed to avoid race conditions. However, they can also lead to deadlocks. What is the key to avoiding this problem?

A.Using as few locks as possible.

B.Carefully paying attention to how locks are acquired and released. ✅

C.Using only semaphores, not mutex locks.

D.Letting the operating system handle all locking.

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: While race conditions are prevented by using locks, the misuse of these locks creates a new problem: deadlocks. Avoiding deadlocks requires a disciplined approach to lock ordering and release. The programmer must ensure that a cycle of waiting threads cannot be created, which is a design problem, not one that the lock itself can solve.

Q34. The dining-philosophers problem is often used to illustrate the need for what in a system?

A.A more powerful CPU

B.A deadlock avoidance algorithm ✅

C.A larger memory

D.A faster network connection

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The dining-philosophers problem, by showing how a simple allocation strategy leads to a deadlock, highlights the need for careful resource management strategies. It is a classic case study for developing and testing algorithms that can prevent, avoid, or detect deadlocks in a system.

Q35. A process requests a resource, uses it, and releases it. If the OS makes a system call to grant the request, what is the role of the system table?

A.To store the process's executable code.

B.To update the resource's state from 'free' to 'allocated' and record the process. ✅

C.To calculate the process's priority.

D.To schedule the next I/O operation.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: When a resource request is granted, the system table must be updated to reflect the new state of the system. It marks the specific resource as 'allocated' and records the process ID of the process that now owns it. This maintains the consistency of the system's resource accounting.

Q36. When a process releases a resource, the system table is updated. What other event might this trigger?

A.The process is immediately terminated.

B.A waiting process for that resource might be woken up and allocated the resource. ✅

C.The system table is deleted.

D.The process is given a higher priority.

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Releasing a resource can unblock a waiting process. The OS will likely check the queue of processes waiting for that resource. If a process is waiting, the OS can allocate the released resource to it, update the system table, and move that process from the waiting state to the ready state. This is a key part of resource management and preventing indefinite postponement.

Q37. If a process requests a resource that is currently allocated to another process, what happens to the system table entry for that resource?

A.It is deleted.

B.It is updated to show the new requesting process.

C.It remains unchanged, showing it is allocated to the current process. ✅

D.It is marked as 'free' temporarily.

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: The system table reflects the current state of resource allocation. Since the resource is still held by the original process, its entry in the table remains unchanged. The new requesting process is simply added to a waiting queue; the table entry itself does not change until the resource is released and reallocated.

Q38. Why is it impossible for a process to request more instances of a resource type than exist in the system?

A.The request system call has a built-in limit.

B.The operating system will reject the request and may terminate the process.

C.It is a logical impossibility; you cannot request what doesn't exist. ✅

D.Such a request would cause an immediate system crash.

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: This is a matter of basic logic and system constraints. A process can only request resources that are physically or logically present in the system. The system table defines the total number of instances of each resource type, and the OS will not grant a request for a resource instance that does not exist.

Q39. A system has a single printer. Process A requests it and is granted. Process B then requests it. What is the state of Process B?

A.It continues execution as normal.

B.It is terminated.

C.It is placed in a waiting queue for the printer. ✅

D.It is given the printer instead of Process A.

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: Since the only printer is already allocated to Process A, Process B's request cannot be granted. The operating system will place Process B into a waiting state, often in a queue associated with the printer resource, until Process A releases it.

Q40. What is the crucial difference between a waiting state caused by a lack of resources and a deadlock?

A.A waiting state is temporary and can resolve; a deadlock is permanent without intervention. ✅

B.A waiting state only involves I/O; a deadlock only involves CPU.

C.A deadlock is always detected by the OS; a waiting state is not.

D.A waiting state is a software bug; a deadlock is a hardware failure.

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: A normal waiting state is a temporary condition. The process is waiting for an event (like I/O completion or resource release) that is expected to occur. A deadlock is a special type of waiting where the event will *never* occur because it's waiting for a release that can only happen as a result of the process's own action, which it cannot take. This makes the wait permanent.

Q41. In the context of the deadlock system model, what does the term 'instance' specifically refer to?

A.A single copy of a resource type, such as one specific CPU or printer. ✅

B.The total number of processes in the system.

C.A single system call.

D.A specific process ID.

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: An 'instance' is a countable unit of a resource type. If a resource type is 'CPU' and the system has two CPUs, then there are two instances of that resource type. Each instance is an individual, usable unit of that resource.

Q42. How does the operating system typically handle a request for a resource that is not immediately available?

A.It denies the request and returns an error code.

B.It adds the requesting process to a queue for that resource. ✅

C.It forcibly takes the resource from the current holder.

D.It automatically assigns a different, equivalent resource.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: When a resource is busy, the standard OS behavior is to block the requesting process. It is added to a queue (a waiting list) for that specific resource. The process will remain blocked in this queue until the resource becomes available and the OS can wake it up.

Q43. What information is typically NOT found in a system table used for resource management?

A.The process ID of the resource holder.

B.The total number of instances of each resource type.

C.The state of a resource (free or allocated).

D.The CPU burst time of each process. ✅

💡 Difficulty: medium | ✅ Correct: D

📖 Explanation: The system table for resource management tracks resources: their type, total instances, current state, and the process that holds them. The CPU burst time is a scheduling parameter and is stored in the Process Control Block (PCB) or similar structure, not the central resource table.

Q44. Why is the release step in the resource utilization sequence critical for preventing deadlocks?

A.It allows the process to request more resources.

B.It makes resources available for other waiting processes. ✅

C.It signals the operating system to terminate the process.

D.It improves the CPU utilization.

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The release step is the only way resources are returned to the system's free pool. If a process fails to release a resource, other processes waiting for it will be blocked indefinitely. This act of releasing is essential for the resource to be reused and is the event that waiting processes are counting on.

Q45. What is a common source of deadlocks related to the use of locks in multithreaded programming?

A.Forgetting to use a lock.

B.Acquiring locks in a different order in different threads. ✅

C.Using too many locks.

D.Using locks that are too fine-grained.

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The classic deadlock scenario in multithreading is the 'lock order inversion'. If Thread A locks lock L1 then attempts to lock L2, while Thread B locks L2 then attempts to lock L1, they can both enter a waiting state. This is a circular wait condition, and it is a primary source of deadlocks in multithreaded applications.

Q46. A system has two identical printers. Process A requests one and is granted printer 1. Process B requests a printer and is granted printer 2. This situation is a:

A.Successful, non-deadlocked allocation. ✅

B.Deadlock.

C.Race condition.

D.Resource starvation.

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: This is a normal and successful allocation. Both processes got the resources they requested. There is no circular wait or blocking because the requests were satisfied immediately. The fact that the printers are identical reinforces that either instance could satisfy the request, and the allocation was made correctly.

Q47. In the deadlock example with three CD-RW drives, if the system had a rule that a process could only request all resources at once, this would prevent the deadlock. Which deadlock condition would this rule prevent?

A.Mutual exclusion

B.Hold and wait ✅

C.No preemption

D.Circular wait

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The 'hold and wait' condition occurs when a process holds some resources and waits for others. If a process must request all resources it needs at once, it will either get them all or wait without holding any. This breaks the 'hold and wait' condition, preventing a scenario where a process holds a drive while waiting for another, which is the exact scenario that led to the deadlock.

Q48. If a process requests a resource that is currently free, the system table is updated to show it is allocated. What is the next step for the process?

A.It is placed in a waiting queue.

B.It can proceed to the 'Use' phase. ✅

C.It must request another resource.

D.It is terminated to free the resource.

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: Once the resource is successfully allocated to the process, the process has satisfied its request. It can now proceed to the next step in the resource utilization sequence, which is to 'Use' the resource to perform its intended task.

Q49. The text mentions that a system may have two CPUs, which is an example of a resource type with multiple instances. How might this affect deadlock prevention?

A.It makes deadlocks impossible.

B.It can make deadlocks more likely because there are more resources to compete for. ✅

C.It is irrelevant to deadlock prevention.

D.It means the CPUs are identical and cannot be part of a deadlock.

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: While having multiple instances of a resource can help avoid deadlocks (by providing alternatives), it also increases complexity. More instances mean more resources to allocate, and the potential for a complex deadlock involving multiple instances and processes increases. However, it is the allocation policy, not the number of instances, that is the primary factor in deadlock prevention.

Q50. What is the relationship between resource classes and deadlocks in the system model?

A.Deadlocks can only occur within a single resource class.

B.Deadlocks can occur across multiple resource classes, both logical and physical. ✅

C.Resource classes are irrelevant to deadlocks.

D.Deadlocks only occur if resource classes are defined incorrectly.

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The examples in the text show deadlocks involving a single class (CD-RWs) and multiple classes (printer and DVD). Deadlocks are a result of circular waits, which can exist between any resources, regardless of their class. Proper definition of classes is important for modeling, but a deadlock can occur across any combination of them.

Q51. A process requests a semaphore, performs a critical operation, and then signals the semaphore. In this scenario, which step is analogous to the 'Release' step?

A.The request for the semaphore.

B.The critical operation.

C.The signal operation. ✅

D.The wait operation.

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: In semaphore operations, `wait()` (or `acquire()`) requests the resource, and `signal()` (or `release()`) releases it. The critical section between them is the 'Use' phase. Therefore, the `signal()` operation directly corresponds to the 'Release' step in the standard resource utilization sequence.

🔗 Related Topics (MCQs)

📝 Deadlocks Introduction in Operating System MCQs 📝 Deadlock Characterization in Operating System MCQs 📝 Necessary Conditions for Deadlock Characterization MCQs 📝 Methods for Handling Deadlocks in Operating System MCQs 📝 Mutual Exclusion Deadlock Prevention MCQs

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