what are some examples of a computer system in an unsafe state and describe how the process could be complete without causing a deadlock.
An example of a computer system in an unsafe state can be illustrated using the resource allocation problem, where multiple processes contend for limited resources. Let's say we have two processes, A and B, and two resources, R1 and R2.
Unsafe State: Initially, process A has acquired resource R1 and requests resource R2, while process B has acquired resource R2 and requests resource R1. This scenario can lead to a deadlock if both processes hold onto their acquired resources and wait indefinitely for the requested resources, causing a halt in the system.
To complete the process without causing a deadlock, we can follow various resource allocation strategies:
1. Resource Ordering: Establish a strict ordering of resources to be acquired. For example, we can enforce that processes must acquire resources in an ascending or descending order of resource numbers. In our example, if both processes adhere to the order of acquiring resources R1 before R2, or vice versa, a deadlock can be avoided. One of the processes can wait until the required resource becomes available.
2. Resource Preemption: Introduce the concept of preemption, where resources can be forcefully taken away from processes to allocate them to other requesting processes. If a process requests a resource that is currently held by another process, the system can preempt the resource from the current holder and grant it to the requesting process. This ensures that at least one process can make progress and avoids deadlock situations.
3. Resource Timeouts: Set a timeout period for resource requests. If a process doesn't receive the requested resource within a predefined timeout, it releases all the resources it holds, performs a rollback, and then retries. This prevents processes from waiting indefinitely for resources, breaking the potential deadlock.
4. Banker's Algorithm: Implement a deadlock avoidance strategy like the Banker's Algorithm. This algorithm uses a mathematical model to analyze the resource allocation requests and ensures that granting resources does not lead to a deadlock situation. It checks for safety by simulating the allocation of resources and verifying if there exists a safe sequence of process execution.
By utilizing these techniques, we can complete the process without causing a deadlock and maintain the safety of the computer system.