Give examples of reusable and consumable resources

1. Give examples of reusable and consumable resources.
2. What are the three conditions that must be present for deadlock to be possible?
3. What are the four conditions that create deadlock?
4. How can the hold-and-wait condition be prevented?

The Correct Answer and Explanation is :

1. Examples of reusable and consumable resources:

• Reusable resources: These are resources that can be used multiple times before they are exhausted. Examples include:
  • Printers
  • CPU time
  • Memory
  • Network bandwidth
  • Hard drives
  • Semaphores
• Consumable resources: These are resources that are used up when they are allocated and cannot be reused. Examples include:
  • Paper in a printer
  • Tokens in a system
  • Fuel in a vehicle
  • CPU cycles in a particular process (if they are not reallocated)
  • Data packets being transferred over a network

1. The three conditions that must be present for deadlock to be possible:

• Mutual Exclusion: At least one resource must be held in a non-shareable mode, meaning only one process can use it at a time.
• Hold and Wait: A process that is holding at least one resource is waiting to acquire additional resources that are currently being held by other processes.
• No Preemption: Resources cannot be forcibly taken away from a process holding them. They can only be released voluntarily by the process.

1. The four conditions that create deadlock:

• Mutual Exclusion: As explained above, at least one resource must be held in a non-shareable mode.
• Hold and Wait: A process holds at least one resource and is waiting to acquire other resources that are currently being held by other processes.
• No Preemption: Resources cannot be preemptively taken from processes; they must be released voluntarily.
• Circular Wait: A set of processes exist such that each process is waiting for a resource that is being held by another process in the set, forming a circular chain of waiting processes.

1. How can the hold-and-wait condition be prevented? The hold-and-wait condition can be prevented by ensuring that processes do not hold any resources while they are waiting for additional resources. This can be accomplished through a method known as resource allocation policy that enforces specific rules for obtaining resources. Specifically, the solution involves requiring processes to request all the resources they need at once, before they begin execution, rather than requesting resources incrementally. Explanation: By enforcing that processes must request all the resources they require for their task in a single atomic request, we eliminate the possibility of holding one resource while waiting for others. In this scenario, once a process is allocated its requested resources, it can proceed without needing to request additional resources. This approach prevents the process from entering a state where it holds a resource and waits for others, thereby eliminating the possibility of deadlock caused by the hold-and-wait condition. This method, while effective in preventing the hold-and-wait condition, may lead to inefficiency. Processes might request resources they do not need immediately, leading to wasted resources or poor resource utilization. Furthermore, the system may need to implement checks to ensure that resource requests do not exceed available resources, which could delay the process from starting. However, in systems where deadlock is a critical concern, such as those handling sensitive operations or in real-time systems, this strategy can be useful for ensuring smooth operation without deadlock.