The main difference between deadlock prevention and deadlock avoidance is that deadlock prevention ensures that at least one of the necessary conditions to cause a deadlock will never occur while deadlock avoidance ensures that the system will not enter an unsafe state.
Deadlock occurs when there are multiple processes. Each process holds a resource while waiting for a resource held by another process. Thus, this kind of situation is a deadlock. A system can go to a deadlock state when mutual exclusion, hold and wait, no preemption, and circular wait conditions occur simultaneously. Here, deadlock prevention and deadlock avoidance are two mechanisms related to deadlocks.
Key Areas Covered
1. What is Deadlock Prevention
– Definition, Functionality
2. What is Dead Avoidance
– Definition, Functionality
3. Difference Between Deadlock Prevention and Deadlock Avoidance
– Comparison of Key Differences
Key Terms
Deadlock, Deadlock Avoidance, Deadlock Prevention
What is Deadlock Prevention
Deadlock prevention is the mechanism to ensure that at least one of the necessary conditions for deadlock can never occur. Usually, it is impossible to implement deadlock prevention. To prevent a deadlock situation, it is not necessary to know the number of all existing resources, availability and requests. Non-blocking synchronization algorithms and serializing tokens are some deadlock prevention algorithms. Furthermore, the resource allocation for deadlock prevention is conservative.
What is Deadlock Avoidance
A system is safe when it is possible to allocate resources to all processes in some order without causing a deadlock. Deadlock is the mechanism to ensure that the system does not enter an unsafe state. In other words, it ensures that the system does not have a deadlock. To avoid a system from reaching an unsafe state, the system should know about the number of existing resources, availability and requests.
The most common technique to avoid deadlock is the banker’s algorithm. It helps to find a safe path to execute all the processes. Also, this algorithm considers the total resources and current requested resources.
Furthermore, in addition to deadlock prevention and avoidance, there is another mechanism called deadlock detection. It detects a deadlock before or after it occurs.
Difference Between Deadlock Prevention and Deadlock Avoidance
Definition
Deadlock prevention is the mechanism to ensure that at least one of the necessary conditions for deadlock can never occur. On the other hand, deadlock avoidance is the mechanism to ensure that the system does not enter an unsafe state. Thus, this is the main difference between deadlock prevention and deadlock avoidance.
Information
In deadlock prevention, the system does not require information of the existing resources, resource availability and resource requests whereas, in deadlock avoidance, the system requires information on the existing resources, resource availability and resource requests to find whether the system is in a safe or unsafe state. Hence, this is another difference between deadlock prevention and deadlock avoidance.
Algorithms
Non-blocking synchronization algorithms and serializing tokens are some deadlock prevention algorithms while Banker’s algorithm is the most common deadlock avoidance algorithm.
Resources
Moreover, the state of resources is an important difference between deadlock prevention and deadlock avoidance. In deadlock prevention, all resources are requested at once while, in deadlock avoidance, the requests for resources are manipulated until at least one safe path is found.
Conclusion
In brief, deadlock is a situation that occurs due to a set of processes in which each process holds a resource and waits to acquire a resource held by another process in the set. Deadlock prevention and deadlock avoidance are two mechanisms related to deadlocks. The main difference between deadlock prevention and deadlock avoidance is that the deadlock prevention ensures that at least one of the necessary conditions to cause a deadlock will never occur, while deadlock avoidance ensures that the system will not enter an unsafe state.
References:
1.“What Is a Deadlock?” Studytonight, Available here.
Image Courtesy:
1.”Deadlock” By Niqueco – Own work (CC0) via Commons Wikimedia
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