Four conditions for deadlock in Operating Systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to name one of the four conditions necessary for a deadlock.

Operating Systems

One of the four conditions for deadlock is called [1].

Drag options to blanks, or click blank then click option'

AResource Allocation

BMutual Exclusion

CProcess Starvation

DThread Synchronization

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing mutual exclusion with resource allocation.

Thinking deadlock happens without exclusive resource use.

Mutual Exclusion means that at least one resource must be held in a non-shareable mode. This is one of the four necessary conditions for deadlock.

2fill in blank

medium

Complete the code to name another condition required for deadlock.

Operating Systems

Another condition for deadlock is [1], where processes hold resources while waiting for others.

Drag options to blanks, or click blank then click option'

ACircular Wait

BDeadlock Prevention

CPreemption

DHold and Wait

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up hold and wait with circular wait.

Thinking preemption is required for deadlock.

Hold and Wait means processes hold at least one resource and wait to acquire additional resources held by others.

3fill in blank

hard

Fix the error in naming the third condition for deadlock.

Operating Systems

The third condition is called [1], where a chain of processes each waits for a resource held by the next.

Drag options to blanks, or click blank then click option'

AResource Starvation

BMutual Exclusion

CCircular Wait

DHold and Wait

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing circular wait with hold and wait.

Using resource starvation which is not a deadlock condition.

Circular Wait means there is a cycle of processes each waiting for a resource held by the next process in the cycle.

4fill in blank

hard

Fill both blanks to complete the last condition for deadlock and its meaning.

Operating Systems

The last condition is [1], which means resources cannot be [2] from a process holding them.

Drag options to blanks, or click blank then click option'

ANo Preemption

BPreempted

CReleased

DAllocated

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing no preemption with resource allocation.

Thinking resources can be taken away forcibly.

No Preemption means that resources cannot be forcibly taken away from a process; the process must release them voluntarily.

5fill in blank

hard

Fill all three blanks to complete the summary of the four conditions for deadlock.

Operating Systems

Deadlock occurs if [1], [2], [3], and circular wait all happen together.

Drag options to blanks, or click blank then click option'

AMutual Exclusion

BHold and Wait

CNo Preemption

DResource Starvation

Attempts:

3 left

💡 Hint

Common Mistakes

Including resource starvation which is not a deadlock condition.

Forgetting no preemption as a condition.

The four conditions for deadlock are Mutual Exclusion, Hold and Wait, No Preemption, and Circular Wait. All must be true for deadlock to occur.

Practice

1. Which of the following is NOT one of the four necessary conditions for a deadlock to occur?

easy

A. Preemptive resource allocation

B. Hold and wait

C. Mutual exclusion

D. Circular wait

Solution

1. Step 1: Recall the four conditions for deadlock

   The four conditions are mutual exclusion, hold and wait, no preemption, and circular wait.

2. Step 2: Identify the incorrect condition

   Preemptive resource allocation is the opposite of no preemption, so it is not a deadlock condition.

3. Final Answer:

   Preemptive resource allocation -> Option A

4. Quick Check:

   Deadlock needs no preemption, not preemption [OK]

Hint: Remember: deadlock needs no preemption, not preemption [OK]

Common Mistakes:

• Confusing no preemption with preemption
• Mixing up circular wait with hold and wait
• Thinking mutual exclusion means all resources are shared

2. Which condition describes the situation where a process holds at least one resource and is waiting to acquire additional resources held by other processes?

easy

A. Mutual exclusion

B. Circular wait

C. No preemption

D. Hold and wait

Solution

1. Step 1: Understand the meaning of hold and wait

   Hold and wait means a process holds some resources and waits for others.

2. Step 2: Match the description to the condition

   The description matches hold and wait exactly.

3. Final Answer:

   Hold and wait -> Option D

4. Quick Check:

   Holding and waiting = Hold and wait [OK]

Hint: Hold some, wait for more means hold and wait [OK]

Common Mistakes:

• Confusing hold and wait with circular wait
• Mixing mutual exclusion with hold and wait
• Thinking no preemption means resources can be taken forcibly

3. Consider four processes P1, P2, P3, and P4 where each process holds a resource and waits for the resource held by the next process in a cycle (P1 waits for P2's resource, P2 waits for P3's, and so on, with P4 waiting for P1's resource). Which deadlock condition does this scenario illustrate?

medium

A. Mutual exclusion

B. Circular wait

C. No preemption

D. Hold and wait

Solution

1. Step 1: Analyze the resource waiting pattern

   Each process waits for a resource held by the next, forming a cycle.

2. Step 2: Identify the deadlock condition

   This cycle of waiting is called circular wait.

3. Final Answer:

   Circular wait -> Option B

4. Quick Check:

   Cycle of waiting = Circular wait [OK]

Hint: Cycle of waiting means circular wait condition [OK]

Common Mistakes:

• Confusing circular wait with hold and wait
• Ignoring the cycle and thinking it's mutual exclusion
• Mixing no preemption with circular wait

4. A system allows preemption of resources but still experiences deadlock. Which of the following conditions is most likely NOT being prevented?

medium

A. Hold and wait

B. Circular wait

C. Mutual exclusion

D. No preemption

Solution

1. Step 1: Understand the effect of preemption

   Preemption means resources can be forcibly taken, so no preemption condition is prevented.

2. Step 2: Identify which condition still causes deadlock

   If deadlock occurs despite preemption, hold and wait or circular wait likely remain.

3. Step 3: Choose the most likely condition

   Hold and wait is often the cause if preemption is allowed but deadlock persists.

4. Final Answer:

   Hold and wait -> Option A

5. Quick Check:

   Preemption allowed but deadlock means hold and wait active [OK]

Hint: If preemption allowed but deadlock, hold and wait remains [OK]

Common Mistakes:

• Assuming no preemption is still active when preemption is allowed
• Confusing mutual exclusion with hold and wait
• Ignoring circular wait as a cause

5. A system designer wants to prevent deadlocks by breaking one of the four conditions. Which condition is easiest to break by requiring processes to request all needed resources at once before execution?

hard

A. No preemption

B. Mutual exclusion

C. Hold and wait

D. Circular wait

Solution

1. Step 1: Understand the effect of requesting all resources at once

   This prevents processes from holding some resources while waiting for others.

2. Step 2: Identify which deadlock condition is broken

   By requiring all resources upfront, hold and wait condition is eliminated.

3. Final Answer:

   Hold and wait -> Option C

4. Quick Check:

   Request all at once breaks hold and wait [OK]

Hint: Request all resources upfront to break hold and wait [OK]

Common Mistakes:

• Thinking mutual exclusion is broken by this method
• Confusing circular wait with hold and wait
• Assuming no preemption is affected