Deadlock

Deadlock

                                                 from geeks for geeks
In a multiprogramming system a number of process compete for limitted number of resources and if a resource is not avilable at that intance then process enter into waiting state.

If a process unable to change its waiting state indefinitely because the resources by it are helds by another waiting process then system is said to be in deadlock.

System model:

• Every process will request for the resources.
• If entertained this process will use the resource.
• Process must be release the resorce after use. 

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Necessary Condition Of Deadlock:

Mutual Exclusion:
At  least one resource type in the system which can be used in non-shared mode that is mutual exclusion(one-at a time/one by one).
Ex- Printer

Hold & Print: 
A process is currently helding  at least one resource and requesting additionnal resources which are being held  by others process.

No Pre-emption:
A resoure can not be pre-empted from a process by any other process resources can releasedoly voluntarvoluntary  by the process holding it.

Circular Wait:
Each process must be waiting for resource which is being held by another process, which in turn is waiting for the first process to release the resource.

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