📝 Safe State in Deadlock Avoidance (51 MCQs)

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

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What is Safe State in Deadlock Avoidance?

Definition:
A state is safe if there exists at least one sequence of processes $\langle P_{\sigma(1)}, P_{\sigma(2)}, ..., P_{\sigma(n)} \rangle$ such that each process can complete using currently available plus held resources.

Example:
With Available $= 3$ and processes needing $\{2, 4, 1\}$ , sequence $\langle P_3, P_1, P_2 \rangle$ is safe because $P_3$ finishes first, releasing resources for others.

Reason:
The safe state concept is the core invariant of avoidance algorithms; maintaining safety ensures the system can always progress to completion without entering a deadlock.

Easy

Medium

Hard

📝 All Safe State in Deadlock Avoidance MCQs

Q1. What is a safe state in the context of deadlock avoidance?

A.A state where no process can request resources

B.A state where the system can allocate resources to each process up to its maximum in some order and avoid deadlock ✅

C.A state where all resources are allocated to processes

D.A state where processes never wait for resources

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: A safe state exists when the system can allocate resources to every process up to its maximum requirement in some order and still avoid deadlock. This ensures there is at least one sequence of process completion that guarantees deadlock freedom regardless of request patterns.

Q2. Which statement accurately describes a safe state?

A.A safe state guarantees that no process will ever request resources

B.A safe state ensures the system can avoid deadlock ✅

C.A safe state means all processes have completed their tasks

D.A safe state requires all resources to be available

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: A safe state ensures the system can avoid deadlock because there exists a sequence in which all processes can complete their maximum resource requirements. However, it doesn't guarantee processes won't request resources; it guarantees the system can handle those requests safely.

Q3. What is the relationship between a safe state and deadlock?

A.A safe state is a deadlocked state

B.A safe state is not a deadlocked state ✅

C.A safe state always leads to deadlock

D.A safe state is equivalent to an unsafe state

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: A safe state is specifically not a deadlocked state. While safe states guarantee deadlock freedom, deadlocked states are always unsafe. The key is that safety implies no deadlock, but the converse isn't true - not all unsafe states are deadlocked.

Q4. Why is a safe state important for deadlock avoidance?

A.It ensures maximum resource utilization

B.It provides a guarantee that the system can avoid deadlock if it stays in safe states ✅

C.It prevents processes from requesting resources

D.It eliminates the need for resource allocation

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: A safe state is fundamental to deadlock avoidance because as long as the system remains in a safe state, it can avoid deadlock. Avoidance algorithms work by ensuring resource allocations only occur when they maintain the system in a safe state, guaranteeing deadlock freedom.

Q5. In deadlock avoidance, what must exist for a state to be considered safe?

A.A process that can complete immediately

B.A safe sequence of processes ✅

C.More available resources than allocated resources

D.A process that holds all resources

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: A state is safe only if there exists at least one safe sequence - an ordering of processes where each can obtain its maximum resource needs from currently available resources plus resources held by preceding processes. The existence of such a sequence is the formal definition of a safe state.

Q6. Which state guarantees the operating system can prevent deadlock?

A.Unsafe state

B.Safe state ✅

C.Deadlocked state

D.Resource-starved state

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: A safe state guarantees the operating system can prevent deadlock through appropriate resource allocation decisions. In an unsafe state, the OS cannot prevent processes from requesting resources in ways that could cause deadlock, as process behavior ultimately determines whether deadlock occurs from that point.

Q7. What is a safe sequence in resource allocation?

A.A sequence of resource requests by a single process

B.A sequence of processes where each can be satisfied by available resources and resources held by previous processes ✅

C.A sequence of resource releases by processes

D.A sequence of operating system instructions

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: A safe sequence is an ordering of processes <P1, P2, ..., Pn> where for each Pi, its remaining resource requests can be satisfied by currently available resources plus resources held by all Pj with j < i. This ensures each process can complete its task and release resources for subsequent processes.

Q8. In a safe sequence <P1, P2, ..., Pn>, what resources can satisfy process P_i's remaining requests?

A.Only resources currently available

B.Only resources held by P_i

C.Resources currently available plus resources held by all Pj where j < i ✅

D.Resources held by all processes except P_i

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: For process P_i in a safe sequence, its remaining requests can be satisfied by currently available resources plus the resources held by all processes Pj that appear earlier in the sequence (j < i). This allows P_i to wait for earlier processes to complete and release their resources.

Q9. What happens when process Pi in a safe sequence cannot obtain resources immediately?

A.The system enters a deadlock

B.Pi can wait until all Pj (j < i) have finished ✅

C.Pi terminates immediately

D.The system becomes unsafe

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: If Pi cannot obtain its needed resources immediately, it can wait until all earlier processes (Pj where j < i) have completed their tasks and released their resources. This is possible because of the safe sequence guarantee that sufficient resources will become available to satisfy Pi's maximum needs.

Q10. What does a process do after completing its designated task in a safe sequence?

A.It requests more resources

B.It returns its allocated resources and terminates ✅

C.It waits for other processes

D.It continues executing indefinitely

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: When a process completes its designated task in a safe sequence, it returns all its allocated resources to the system and terminates. This releases resources that can then be used by subsequent processes in the sequence, enabling the chain of completions that defines a safe sequence.

Q11. How does the completion of process Pi benefit subsequent processes in a safe sequence?

A.It increases the priority of subsequent processes

B.It makes additional resources available for subsequent processes ✅

C.It reduces the maximum needs of subsequent processes

D.It prevents subsequent processes from requesting resources

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: When process Pi completes and returns its allocated resources, these resources become available to subsequent processes (Pi+1, etc.). This availability of released resources is crucial for satisfying the remaining requests of later processes in the safe sequence, allowing the entire sequence to complete.

Q12. What condition must be satisfied for each Pi in a safe sequence?

A.Pi must have the highest priority

B.The resources Pi can still request must be satisfyable by available resources plus resources held by Pj where j < i ✅

C.Pi must request resources in alphabetical order

D.Pi must complete before P(i-1)

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The formal condition is that Pi's remaining resource requests can be satisfied by currently available resources plus resources held by all preceding processes (Pj with j < i). This ensures that even if Pi must wait, it will eventually receive resources when earlier processes complete, making the sequence valid.

Q13. If a safe sequence exists for the current allocation state, what is guaranteed?

A.All processes will complete immediately

B.The system is in a safe state ✅

C.No resource requests will be made

D.The system will never allocate resources

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The existence of a safe sequence is the formal definition of a safe state. It guarantees that there is an ordering where all processes can obtain their maximum resource needs and complete. This doesn't mean they will follow that order, but it ensures the system can avoid deadlock if it maintains this state.

Q14. In a safe sequence, when can Pi obtain all its needed resources?

A.Immediately upon request

B.After all Pj where j > i have finished

C.After all Pj where j < i have finished ✅

D.After Pi releases its resources

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: Pi can obtain all its needed resources after all earlier processes (Pj with j < i) have finished and released their resources. The safe sequence guarantees that when these earlier processes complete, there will be enough resources to satisfy Pi's maximum needs, allowing it to proceed to completion.

Q15. What is the role of 'currently available resources' in defining a safe sequence?

A.They are ignored for safety checking

B.They are the only resources that can satisfy requests immediately

C.They combined with resources from earlier processes to satisfy each Pi ✅

D.They determine process priority

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: Currently available resources, combined with resources held by all earlier processes in the sequence, are used to satisfy each Pi's remaining requests. This combination is essential because it allows earlier processes to complete and release resources that, together with already available resources, can satisfy the needs of subsequent processes.

Q16. What is an unsafe state in deadlock avoidance?

A.A state where a deadlock has already occurred

B.A state where no safe sequence exists ✅

C.A state where all resources are allocated

D.A state where processes have completed

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: An unsafe state is one where no safe sequence exists. This means there is no ordering of processes that guarantees all can complete their maximum resource requirements. While an unsafe state hasn't necessarily deadlocked yet, it could potentially lead to deadlock depending on future resource requests.

Q17. Which statement correctly describes the relationship between unsafe states and deadlocks?

A.All unsafe states are deadlocked states

B.No unsafe states are deadlocked states

C.A deadlocked state is an unsafe state, but not all unsafe states are deadlocked ✅

D.Unsafe states and deadlocked states are completely unrelated

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: A deadlocked state is always an unsafe state, but not all unsafe states are deadlocked. An unsafe state has the potential to lead to deadlock, but deadlock hasn't necessarily occurred yet. This distinction is important because the system can sometimes recover from unsafe states before deadlock occurs.

Q18. What controls the outcome when the system enters an unsafe state?

A.The operating system scheduler

B.The behavior of the processes ✅

C.The number of available resources

D.The resource allocation algorithm

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: When the system is in an unsafe state, the operating system cannot prevent processes from requesting resources in ways that could cause deadlock. The behavior of the processes themselves determines whether an actual deadlock occurs from an unsafe state, as the OS can only control resource allocation decisions.

Q19. Why might a system be in an unsafe state but not deadlocked?

A.Because processes may not request all their resources ✅

B.Because the system can always recover

C.Because unsafe states never lead to deadlock

D.Because processes are always cooperative

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: A system can be in an unsafe state without being deadlocked because processes may not actually request their maximum resource needs. The unsafe state indicates the potential for deadlock if certain request patterns occur, but actual deadlock requires processes to make the specific requests that create circular waiting.

Q20. What is the key characteristic of an unsafe state?

A.All processes are waiting for resources

B.No safe sequence exists for the current allocation state ✅

C.All resources are available

D.Processes cannot be allocated any more resources

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: An unsafe state is characterized by the absence of any safe sequence. This means there is no ordering of processes that would guarantee all can complete their maximum resource requirements. However, this doesn't mean deadlock has occurred - it only means the system has entered a potentially dangerous region where deadlock could happen depending on future process behavior.

Q21. What happens when the operating system grants a request that leads to an unsafe state?

A.The system immediately deadlocks

B.The system may or may not deadlock depending on future process behavior ✅

C.The system terminates all processes

D.The system rolls back to the previous state

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Granting a request that leads to an unsafe state doesn't guarantee immediate deadlock. Deadlock will occur only if processes subsequently request resources in a specific pattern that creates circular waiting. The OS cannot prevent this outcome once in an unsafe state, as process behavior, not OS control, determines what happens next.

Q22. How does the system determine if a state is unsafe?

A.By checking if resources are available

B.By verifying all processes have completed

C.By attempting to find a safe sequence ✅

D.By measuring process waiting times

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: The system determines if a state is unsafe by attempting to find a safe sequence. If no such sequence exists, the state is unsafe. This is done by checking if there is an ordering of processes where each can obtain its maximum resource needs from available resources plus resources held by earlier processes.

Q23. What is the relationship between safe, unsafe, and deadlocked states?

A.Safe states are a subset of unsafe states

B.Deadlocked states are a subset of unsafe states ✅

C.Safe states and deadlocked states are the same

D.Unsafe states are a subset of deadlocked states

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Deadlocked states are a subset of unsafe states. Every deadlocked state is unsafe, but not every unsafe state is deadlocked. Safe states are completely separate from deadlocked states - a safe state cannot be deadlocked, and a deadlocked state is always unsafe. This hierarchical relationship is crucial for understanding deadlock avoidance.

Q24. Why is it possible to go from a safe state to an unsafe state?

A.Because processes always request resources randomly

B.Because granting certain resource requests can make the system unsafe ✅

C.Because the system loses resources

D.Because processes terminate unexpectedly

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: A system can transition from safe to unsafe when the operating system grants a resource request that, while making resources available to one process, creates a situation where no safe sequence exists. This typically happens when resources are allocated in a way that prevents some processes from ever obtaining their maximum needs.

Q25. What happens when a system moves from a safe to an unsafe state?

A.The system immediately deadlocks

B.The system can no longer guarantee deadlock avoidance ✅

C.The system crashes

D.All processes are terminated

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: When a system moves from a safe to an unsafe state, it loses the guarantee of deadlock avoidance. While deadlock may not have occurred yet, the system can no longer ensure that processes won't request resources in patterns that create deadlock. The behavior of processes now determines whether deadlock occurs.

Q26. What is the relationship between safe states and deadlocks?

A.Safe states can contain deadlocks

B.Safe states are the same as deadlocked states

C.Safe states do not contain deadlocks ✅

D.Safe states always lead to deadlocks

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: A safe state is explicitly not a deadlocked state. The definition of a safe state guarantees that there exists a sequence where all processes can complete without deadlock. Therefore, a state cannot be both safe and deadlocked - they are mutually exclusive concepts. Safe states represent deadlock-free configurations.

Q27. What does an operating system aim for in deadlock avoidance regarding state spaces?

A.To remain in the safe state region ✅

B.To operate in the unsafe state region

C.To operate exclusively in the deadlocked state region

D.To randomly move between state regions

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: In deadlock avoidance, the operating system aims to keep the system in the safe state region at all times. By ensuring every resource allocation maintains the system in a safe state, the OS guarantees that deadlock can be avoided regardless of future process requests, providing the best possible protection against deadlock.

Q28. If a system is in an unsafe state, what can the operating system do?

A.Prevent deadlock by controlling resource requests

B.Only hope that processes don't cause deadlock ✅

C.Force all processes to release resources

D.Terminate all processes immediately

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: In an unsafe state, the operating system cannot prevent processes from requesting resources in ways that could cause deadlock. The behavior of the processes controls whether deadlock occurs. The OS can only make decisions about granting requests; once in an unsafe state, it loses the ability to guarantee deadlock avoidance, as process behavior determines the outcome.

Q29. In the tape drive example, how many total tape drives does the system have?

A.10

B.12 ✅

C.9

D.14

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The system has twelve magnetic tape drives total. This is the starting point for the example, with three processes P0, P1, and P2 having maximum needs of 10, 4, and 9 tape drives respectively, and current holdings that reduce available drives to 3 at the initial time t0.

Q30. What are the maximum tape drive requirements for processes P0, P1, and P2 respectively?

A.38269

B.40090 ✅

C.39913

D.40425

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: Process P0 requires up to 10 tape drives, process P1 requires up to 4 tape drives, and process P2 requires up to 9 tape drives. These maximum needs are declared a priori and used by the system to determine if the current allocation state is safe.

Q31. At time t0 in the tape drive example, what is the allocation status of the three processes?

A.P0:5, P1:2, P2:2 ✅

B.P0:10, P1:4, P2:9

C.P0:2, P1:5, P2:2

D.P0:2, P1:2, P2:5

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: At time t0, process P0 holds 5 tape drives, process P1 holds 2 tape drives, and process P2 holds 2 tape drives. This totals 9 allocated drives, leaving 3 free tape drives in the system with 12 total drives.

Q32. What is the safe sequence demonstrated at time t0 in the tape drive example?

A.<P2, P0, P1>

B.<P1, P0, P2> ✅

C.<P0, P1, P2>

D.<P2, P1, P0>

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The safe sequence at time t0 is <P1, P0, P2>. Process P1 can immediately get its remaining 2 drives, complete, and return them. Then P0 can get its remaining 5 drives, complete, and return them. Finally, P2 can get its remaining 7 drives and complete. This sequence verifies the system is in a safe state.

Q33. In the tape drive example, why is <P1, P0, P2> a safe sequence at time t0?

A.Because P1 requires the most resources

B.Because P1 can complete first, then P0, then P2 ✅

C.Because P1 has the highest priority

D.Because P1 holds the most resources

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: At time t0, P1 only needs 2 more drives (maximum 4, currently holds 2), which are available (3 free). P1 can complete, returning 4 drives (now 5 available). Then P0 needs 5 more (10 maximum, holds 5), which are available. After P0 completes, 10 drives are available, enough for P2's remaining 7. This ordering makes it safe.

Q34. What happens when P2 requests one more tape drive at time t1 in the example?

A.The system remains in a safe state

B.The system enters an unsafe state ✅

C.A deadlock immediately occurs

D.The system crashes

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: When P2 requests and is allocated one more tape drive at time t1, the system enters an unsafe state. With P2 now holding 3 drives (needing 6 more), P0 needing 5 more, and only 2 free drives, no safe sequence exists. However, deadlock hasn't occurred yet - the system is just in an unsafe state with potential for deadlock.

Q35. After P2 receives the additional tape drive at time t1, why can't the system guarantee deadlock avoidance?

A.Because resources are insufficient for all processes

B.Because only P1 can complete, but then insufficient resources remain for P0 and P2 ✅

C.Because P2 has the highest priority

D.Because the operating system loses control

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: After P2 gets the additional drive, only P1 can complete (needs 2 drives, with 2 free). After P1 returns its 4 drives, only 4 drives are free. P0 needs 5 more drives and P2 needs 6 more, so they'd have to wait for each other. Since P0 and P2 could request these remaining drives simultaneously, the system may enter deadlock.

Q36. What was the mistake in the tape drive example that led to an unsafe state?

A.Granting the request from P2 for one more tape drive ✅

B.Granting the request from P1 for more tape drives

C.Not allocating enough resources initially

D.Scheduling P0 incorrectly

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: The mistake was granting P2's request for one more tape drive at time t1. The system should have made P2 wait until either P0 or P1 had finished and released its resources. By granting this request, the system moved from a safe to an unsafe state, potentially leading to deadlock if P0 and P2 request their remaining resources.

Q37. What should the system have done in the tape drive example when P2 requested the additional drive?

A.Granted the request immediately

B.Made P2 wait until P0 or P1 finished ✅

C.Denied the request permanently

D.Given the drive to P0 instead

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The system should have made P2 wait until either P0 or P1 had finished and released its resources. By delaying P2's request, the system could have maintained its safe state. When P1 completes and releases resources, P2 could then be granted the additional drive while still maintaining system safety.

Q38. In the tape drive example, what is the sequence of completions that makes the initial state safe?

A.P1 completes, then P0 completes, then P2 completes ✅

B.P0 completes, then P1 completes, then P2 completes

C.P2 completes, then P0 completes, then P1 completes

D.P1 completes, then P2 completes, then P0 completes

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: The safe sequence is P1 completes first, then P0, then P2. P1 can complete immediately with its remaining 2 drives. After P1 releases its 4 drives, P0 can get its remaining 5 drives and complete. After P0 releases its 10 drives, P2 can get its remaining 7 drives and complete. This ordering ensures all processes complete.

Q39. How many free tape drives are available at time t0 in the example?

A.3 ✅

B.5

C.2

D.4

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: At time t0, there are 3 free tape drives. This is calculated as: 12 total drives - 5 (P0 holds) - 2 (P1 holds) - 2 (P2 holds) = 3 free drives. These 3 free drives are the key resource for determining if the system can remain in a safe state.

Q40. What maximum number of tape drives can process P2 need in the example?

A.4

B.9 ✅

C.10

D.12

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: Process P2 may need up to 9 tape drives. This maximum is declared a priori and is used in safety checking. At time t0, P2 holds 2 drives and could request up to 7 more (to reach its maximum of 9), which is why the availability of drives after P1 and P0 complete is critical for safety.

Q41. Why does the system enter an unsafe state after granting P2's additional request at time t1?

A.Because P2 now holds more than its maximum

B.Because there are not enough resources to guarantee completion of all processes ✅

C.Because P0 requests resources immediately

D.Because the system runs out of memory

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: After granting P2's request, only P1 can complete. After P1 completes, only 4 drives are available. P0 needs 5 more and P2 needs 6 more to reach their maximums. If both request their remaining resources, deadlock occurs because neither can get enough to complete. This lack of a completion sequence defines the unsafe state.

Q42. How do deadlock avoidance algorithms ensure the system never deadlocks?

A.By always granting resource requests immediately

B.By ensuring the system remains in a safe state ✅

C.By preventing any process from requesting resources

D.By terminating processes that request resources

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: Avoidance algorithms ensure the system never deadlocks by maintaining the system in a safe state at all times. This is achieved by only granting resource requests that keep the system safe, and making processes wait if granting their request would lead to an unsafe state.

Q43. When must the system decide whether a resource request should be granted or the process should wait?

A.Only when resources are scarce

B.Whenever a process requests a resource that is currently available ✅

C.Only for the first request of each process

D.Whenever resources are requested

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The system must make this decision whenever a process requests a resource that is currently available. While the resource is available, the system must determine if granting it would maintain the safe state. If granting it would lead to an unsafe state, the process must wait even though the resource is currently available.

Q44. What happens when a process requests an available resource but granting it would lead to an unsafe state?

A.The resource is granted anyway

B.The process must wait ✅

C.The process is terminated

D.The system crashes

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: If granting a request would lead to an unsafe state, the process must wait even though the resource is currently available. This is the key tradeoff in deadlock avoidance: sometimes making processes wait for available resources is necessary to maintain system safety and prevent possible deadlocks.

Q45. What is the primary tradeoff in using deadlock avoidance algorithms?

A.Increased CPU usage for less memory

B.Lower resource utilization for guaranteed deadlock freedom ✅

C.Higher throughput for increased complexity

D.Simpler implementation for lower reliability

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The primary tradeoff is lower resource utilization for guaranteed deadlock freedom. Because processes may have to wait for available resources to maintain a safe state, resource utilization can be lower than it would be otherwise. However, the benefit is guaranteed deadlock avoidance, making the system more reliable.

Q46. What must the system ensure initially for deadlock avoidance algorithms to work?

A.All resources are available

B.The system starts in a safe state ✅

C.No processes are running

D.All resources are allocated

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: For deadlock avoidance algorithms to work, the system must start in a safe state. The algorithm then ensures all subsequent resource allocations maintain this safe state. If the system started in an unsafe state, the algorithm couldn't guarantee deadlock avoidance, as it would already be in a situation where no safe sequence exists.

Q47. Why might resource utilization be lower when using deadlock avoidance algorithms?

A.Because processes run slower

B.Because processes may have to wait for available resources ✅

C.Because resources are not used at all

D.Because processes request more resources than needed

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Resource utilization may be lower because processes may have to wait for resources even when they are available. This happens when granting the request would move the system to an unsafe state. The process waits until the request can be granted safely, potentially leaving resources idle during this waiting period.

Q48. What condition must be met for a resource request to be granted in deadlock avoidance?

A.The process must have the highest priority

B.The allocation must leave the system in a safe state ✅

C.The resource must have been used before

D.The process must have completed its previous request

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: A resource request is granted only if the resulting allocation leaves the system in a safe state. This is the fundamental rule of deadlock avoidance: only make allocations that maintain safety. If granting the request would lead to an unsafe state, the request is denied and the process must wait, regardless of resource availability.

Q49. In deadlock avoidance, what does the system do when it receives a request for an available resource?

A.Immediately allocates the resource

B.Checks if allocation would maintain a safe state ✅

C.Always denies the request

D.Allocates only if the process has a high priority

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: When receiving a request for an available resource, the system must check if the allocation would maintain a safe state. This involves evaluating whether, after granting the request, there exists a safe sequence for all processes. Only if this condition is satisfied does the system allocate the resource to the requesting process.

Q50. What is the effect of making processes wait for available resources in deadlock avoidance?

A.It increases system throughput

B.It guarantees deadlock freedom ✅

C.It eliminates the need for resource allocation

D.It simplifies the scheduling algorithm

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Making processes wait for available resources, when necessary, guarantees deadlock freedom by maintaining the system in a safe state. While this may reduce resource utilization and throughput, the primary benefit is the guarantee that deadlock will never occur, making the system more reliable and predictable.

Q51. What happens if a process requests a resource that is currently unavailable in deadlock avoidance?

A.The resource is preempted from another process

B.The process waits immediately ✅

C.The request is denied permanently

D.The system terminates the process

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: If a requested resource is currently unavailable, the process must wait regardless of safety considerations. The process can only acquire the resource when it becomes available and when granting it maintains system safety. This is part of the normal resource allocation process, not specific to deadlock avoidance decisions.

🔗 Related Topics (MCQs)

📝 Deadlocks Introduction in Operating System MCQs 📝 Deadlocks System Model in Operating System MCQs 📝 Deadlock Characterization in Operating System MCQs 📝 Necessary Conditions for Deadlock Characterization MCQs 📝 Methods for Handling Deadlocks in Operating System MCQs

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