In general, there is a set of waiting processes, P =, such that P1 is waiting for a resource held by P2, P2 is waiting for a resource held by P3 and so on till PN is waiting for a resource held by P1. Circular Wait: A process must be waiting for a resource which is being held by another process, which in turn is waiting for the first process to release the resource.This can be achieved through various methods such as resource allocation, using a two-phase lock protocol, and time-out-based mechanisms. No Preemption: The operating system must not de-allocate resources once they have been allocated they must be released by the holding process voluntarily. Deadlock Avoidance: Deadlock avoidance is a technique used in operating systems to prevent deadlocks from occurring by ensuring that the necessary conditions for a deadlock are never met.Hold and Wait or Resource Holding: A process is currently holding at least one resource and requesting additional resources which are being held by other processes.One necessary condition for deadlock is, which states that a process must be holding one resource and waiting to acquire additional resources. Mutual section from the resource point of view is the fact that a resource can never be used by more than. Lets see how we can prevent each of the conditions.

It involves designing the system in such a way that at least one of the necessary conditions for deadlock cannot. The same happens with deadlock, if we can be able to violate one of the four necessary conditions and dont let them occur together then we can prevent the deadlock. reusable fixed number of units neither created nor destroyed request -> use -> release -> repeat. One necessary condition for deadlock is, which states that at least one resource must be held in a nonsharable mode. Deadlock prevention is a technique used in operating systems to ensure that deadlocks, which are situations where two or more processes are unable to proceed because each is waiting for the other to release a resource, do not occur. Only one process can use the resource at any given instant of time. These topics are from Chapters 3 (Deadlock) in Advanced Concepts in OS. Mutual Exclusion: At least one resource must be non-shareable.A deadlock situation can arise if and only if all of the following conditions hold simultaneously in a system:

Necessary conditions for deadlock in os