#DEADLOCK COMPUTER SCIENCE WINDOWS#

Preempt resources from the process when resources required by other high priority processes.Įach resource will be assigned with a numerical number.

The process will make a new request for resources after releasing the current set of resources.

for example, if a process requires printer at a later time and we have allocated printer before the start of its execution printer will remain blocked till it has completed its execution.

Allocate all required resources to the process before the start of its execution, this way hold and wait condition is eliminated but it will lead to low device utilization.

It is not possible to dis-satisfy the mutual exclusion because some resources, such as the tape drive and printer, are inherently non-shareable. We can prevent Deadlock by eliminating any of the above four conditions.

#DEADLOCK COMPUTER SCIENCE WINDOWS#

This is the approach that both Windows and UNIX take.Īs discussed in the previous post, deadlock has following characteristics. Ignore the problem altogether: If deadlock is very rare, then let it happen and reboot the system.

Deadlock detection and recovery: Let deadlock occur, then do preemption to handle it once occurred.We use Banker’s algorithm (Which is in-turn a gift from Dijkstra) in order to avoid deadlock. We need to ensure that all information about resources which process will need are known to us prior to execution of the process. By using strategy of “Avoidance”, we have to make an assumption. One can zoom into each category individually, Prevention is done by negating one of above mentioned necessary conditions for deadlock.Īvoidance is kind of futuristic in nature. Deadlock prevention or avoidance: The idea is to not let the system into a deadlock state.Circular Wait: A set of processes are waiting for each other in circular form.No Preemption: A resource cannot be taken from a process unless the process releases the resource.Hold and Wait: A process is holding at least one resource and waiting for resources.Mutual Exclusion: One or more than one resource are non-shareable (Only one process can use at a time).For example, in the below diagram, Process 1 is holding Resource 1 and waiting for resource 2 which is acquired by process 2, and process 2 is waiting for resource 1.ĭeadlock can arise if the following four conditions hold simultaneously (Necessary Conditions) A similar situation occurs in operating systems when there are two or more processes that hold some resources and wait for resources held by other(s). Introduction of Deadlock in Operating SystemĪ process in operating systems uses different resources and uses resources in the following way.ĭeadlock is a situation where a set of processes are blocked because each process is holding a resource and waiting for another resource acquired by some other process.Ĭonsider an example when two trains are coming toward each other on the same track and there is only one track, none of the trains can move once they are in front of each other.

Deadlock computer science