Deadloc-Lec2

1.1 Methods for Handling Deadlocks
Generally speaking, we can deal with the deadlock problem in one of two ways:
• We can use a protocol to prevent or avoid deadlocks, ensuring that the system will never enter a deadlocked state.
• We can allow the system to enter a deadlocked state, detect it, and recover.
To ensure that deadlocks never occur, the system can use either a deadlock- prevention or a deadlock-avoidance scheme. Deadlock prevention provides a set of methods for ensuring that at least one of the necessary conditions cannot hold. These methods prevent deadlocks by constraining how requests for resources can be made.
Deadlock avoidance requires that the operating system be given in advance additional information concerning which resources a process will request and use during its lifetime. With this additional knowledge, it can decide for each request whether or not the process should wait. To decide whether the current request can be satisfied or must be delayed, the system must consider the resources currently available, the resources currently allocated to each process, and the future requests and releases of each process.
If a system does not employ either a deadlock-prevention or a deadlock- avoidance algorithm, then a deadlock situation may arise. In this environment, the system can provide an algorithm that examines the state of the system to determine whether a deadlock has occurred and an algorithm to recover from the deadlock (if a deadlock has indeed occurred).