A deadlock situation can arise if and only if the following four conditions hold simultaneously in a system-
Mutual Exclusion: At least one resource is held in a non-sharable mode that is only one process at a time can use the resource. If another process requests that resource, the requesting process must be delayed until the resource has been released.
Hold and Wait:There must exist a process that is holding at least one resource and is waiting to acquire additional resources that are currently being held by other processes.
No Preemption: Resouces cannot be preempted; that is, a resource can only be released voluntarily by the process holding it, after the process has completed its task.
Circular Wait: There must exist a set {p0, p1,.....pn} of waiting processes such that p0 is waiting for a resource which is held by p1, p1 is waiting for a resource which is held by p2,..., pn-1 is waiting for a resource which is held by pn and pn is waiting for a resource which is held by p0.
On some platforms (unix, for example) devices are handled as special files.
DEADLOCK PREVENTION:Preventing deadlocks by constraining how requests for resources can be made in the system and how they are handled (system design).The goal is to ensure that at least one of the necessary conditions for deadlock can never hold.DEADLOCK AVOIDANCE:The system dynamically considers every request and decides whether it is safe to grant it at this point,The system requires additional apriori information regarding the overall potential use of each resource for each process.Allows more concurrency.
There are four strategies of dealing with deadlock problem:1. The Ostrich ApproachJust ignore the deadlock problem altogether.2. Deadlock Detection and RecoveryDetect deadlock and, when it occurs, take steps to recover.3. Deadlock AvoidanceAvoid deadlock by careful resource scheduling.4. Deadlock PreventionPrevent deadlock by resource scheduling so as to negate at least one of the four conditions.
Deadlock prevention is the name of the technique that is designed to get rid of deadlocks by changing the specifications of the system , that is the system design change. This is , basically , about how requests about resources are made and how they are permitted. However , deadlock avoidance is a technique that aims to check deadlock possibility dynamically and decides whether it is safe to grant a resource or not. It ,definitely , needs extra information about potential use of resources for each process. Deadlock Prevention: Preventing deadlocks by constraining how requests for resources can be made in the system and how they are handled (system design). The goal is to ensure that at least one of the necessary conditions for deadlock can never hold. Deadlock Avoidance: The system dynamically considers every request and decides whether it is safe to grant it at this point, The system requires additional apriori information regarding the overall potential use of each resource for each process. Allows more concurrency. Similar to the difference between a traffic light and a police officer directing traffic.
The antonym for deadlock is agreement.
Holy Deadlock was created in 1934.
Deadlock - film - was created in 1931.
Wedlock Deadlock was created in 1947.
House of Dreams - 2004 To Deadlock or Not to Deadlock 1-3 was released on: USA: 22 January 2004
deadlock handling by 2phase protocol
Holy Deadlock has 311 pages.
Wolves - Deadlock album - was created in 2007.