What do you mean by deadlock prevention? A computer has six tape drives with processes competing for them. Each process needs two tape drives for each value of n.

Deadlock Prevention:

Deadlock prevention is a technique used in operating systems to ensure that deadlocks never occur in a system. Unlike deadlock detection and recovery, which allow deadlocks to occur and then attempt to recover from them, deadlock prevention aims to prevent deadlocks from happening in the first place.

In deadlock prevention, the system imposes restrictions on how resources are allocated to processes to prevent them from entering a deadlock state. This is achieved by ensuring that at least one of the necessary conditions for a deadlock to occur is never met.

Necessary Conditions for a Deadlock:

There are four necessary conditions that must be met for a deadlock to occur:

1. Mutual Exclusion: Each resource is held by only one process at a time.
2. Hold and Wait: A process holding at least one resource is waiting to acquire additional resources held by other processes.
3. No Preemption: A resource cannot be forcibly taken away from a process that is holding it.
4. Circular Wait: A closed chain of processes exists, where each process is waiting for a resource held by the next process in the chain.

Deadlock Prevention Techniques:

To prevent deadlocks, the system can employ various techniques, such as:

1. Resource Ordering: Resources are assigned a linear order, and processes must request resources in that order. This ensures that no circular wait can occur.
2. Resource Allocation: The system tracks the allocation of resources to processes and ensures that no process is allocated more resources than it needs.
3. Hold and Wait Prevention: When a process requests a resource that is held by another process, the requesting process is put on hold until the resource becomes available. This prevents the hold-and-wait condition from occurring.
4. Process Scheduling: The system schedules processes in a way that minimizes the likelihood of deadlocks. For example, processes that are likely to request the same resources are scheduled to run at different times.

Deadlock Prevention in a System with Six Tape Drives:

Consider a computer system with six tape drives and multiple processes competing for them. Each process needs two tape drives for each value of n. To prevent deadlocks in this system, the following measures can be taken:

1. Resource Ordering: The tape drives are assigned a linear order, such as T1, T2, T3, T4, T5, and T6.
2. Resource Allocation: Each process is only allowed to allocate two tape drives at a time.
3. Hold and Wait Prevention: When a process requests a tape drive that is held by another process, the requesting process is put on hold until the resource becomes available.
4. Process Scheduling: Processes are scheduled in a way that minimizes the likelihood of deadlocks. For example, processes that are likely to request the same tape drives are scheduled to run at different times.

By implementing these measures, the system can prevent deadlocks from occurring and ensure that all processes can access the resources they need to execute.