What are the differences between deadlock avoidance and deadlock prevention in operating systems?

Answer 1

Deadlock Prevention:

o Preventing deadlocks by constraining how

requests for resources can be made in the system and how

they are handled (system design).

o The goal is to ensure that at least one of the

necessary conditions for deadlock can never hold.

*

Deadlock Avoidance:

o The system dynamically considers every request

and decides whether it is safe to grant it at this point,

o The system requires additional apriori

information regarding the overall potential use of each

resource for each process.

o Allows more concurrency.

Similar to the difference between a traffic light

and a police officer directing traffic.

* Deadlock deduction:-

Often, neither avoidance nor deadlock

prevention may be used. Instead deadlock detection and

process restart are used by employing an algorithm that

tracks resource allocation and process states, and rolls

back and restarts one or more of the processes in order to

remove the deadlock. Detecting a deadlock that has already

occurred is easily possible since the resources that each

process has locked and/or currently requested are known to

the resource scheduler or OS.

Detecting the possibility of a deadlock before it occurs is

much more difficult and is, in fact, generally undecidable,

because the halting problem can be rephrased as a deadlock

scenario. However, in specific environments, using specific

means of locking resources, deadlock detection may be

decidable. In the general case, it is not possible to

distinguish between algorithms that are merely waiting for a

very unlikely set of circumstances to occur and algorithms

that will never finish because of deadlock.

Deadlock detection techniques include, but is not limited

to, Model checking. This approach constructs a Finite

State-model on which it performs a progress analysis and

finds all possible terminal sets in the model. These then

each represent a deadlock.