In this blog we will learn about the deadlock in operating system, first, we will define deadlock, and we will have a proper section dedicated to the question what is deadlock in os? followed by some necessary condition for deadlock with proper explanation and various methods for handling deadlock. We will learn all about the deadlock in os from scratch in this blog.
What is Deadlock in Operating System?
In this section, we will define deadlock in os. As we all know in a system when a process run it requires numerous resources like file, storage, CPU, input, output devices, etc. And the process releases the resources after completing its execution and the other process will take the resources after that but this is the ideal case that does not happen generally as all the processes compete for the resources and there is a high chance that the resource that one process required is currently in use by other process and that process is not gonna leave the resources until its execution is completed and the waiting will be infinite. This may arise a deadlock situation. We will learn all about the necessary condition for deadlock further in this article.
A deadlock is a situation in an operating system where two or more processes are unable to proceed because each is waiting for one of the others to release a resource. These processes are said to be in a "deadlocked" state. Deadlocks can occur in a variety of situations, such as when two processes are trying to acquire locks on shared resources in different orders. And because of deadlock, no process gets executed.
When a deadlock occurs, all of the processes involved are stuck and unable to make progress. This can lead to poor system performance and potentially cause the system to become unresponsive. To prevent deadlocks, an operating system can use various techniques such as lock order, timeout-based mechanisms, and deadlock detection and recovery algorithms. Deadlock prevention methods are designed to ensure that a set of conditions known as the "necessary conditions for deadlock" can never be met. Deadlock detection and recovery methods, on the other hand, monitor the state of the system and detect when a deadlock has occurred, and then take action to resolve the deadlock.
Necessary Condition For Deadlock
There are certain conditions that must be followed for a deadlock to occur as just not getting resources on time does not create a deadlock in os. There are four necessary condition for deadlock in os. Those conditions are explained below:
- Mutual Exclusion: This means all the resources can not use the same resource simultaneously i.e, a resource can only be used by a single process at a single time frame. By summarising at least one resource must be non-sharable for a deadlock to occur.
- Hold and Wait: In this, a process is holding atleast a single resource and is waiting to acquire another resource which is acquired by some other process.
- No Preemption: We cannot forcefully take the resources from the process the process must leave the resources voluntarily after the complete execution.
- Circular Wait: There must be a circular chain of processes, where each process is waiting for a resource held by the next process in the chain. Let’s understand this with an example suppose we have two processes p1 and p2 and p1 is holding the resource1 and p2 wants resource 1 and p1 is waiting for resource 2 so if it gets resource 2 it will complete the execution and release both the resources but resource 2 is held by p2 as it is waiting for resource 1 so this is one example of circular wait.
Methods for Handling Deadlock
We need to handle deadlock as they may create a lot of problems There are many methods There are many methods for handling deadlock that is available. We will discuss all of them in this section of the blog.
- Deadlock Prevention: Deadlock prevention is a technique used by operating systems to prevent deadlocks from occurring by ensuring that the necessary conditions for a deadlock are never met. This can be achieved through various methods such as lock order, timeout-based mechanisms, and resource allocation. Deadlock prevention is considered to be a more effective approach than deadlock detection and recovery as it eliminates the possibility of deadlocks altogether. However, it can be difficult to implement in practice, and it may not always be possible or practical to prevent deadlocks completely. This technique is very costly so most organizations do not use it unless its the top priority of the organization to make the system deadlock-free.
- Deadlock Avoidance: Deadlock avoidance is a technique used in operating systems to prevent deadlocks from occurring by ensuring that the necessary conditions for a deadlock are never met. This can be achieved through various methods such as resource allocation, using a two-phase lock protocol, and time-out-based mechanisms. Deadlock avoidance is considered to be a more effective approach than deadlock detection and recovery, as it eliminates the possibility of deadlocks altogether. However, it can be difficult to implement in practice and may not always be possible or practical to avoid deadlocks completely. Here we must have all the knowledge of the resources prior to their allocation so we can see ether this allocation will cause a deadlock or not.
- Deadlock detection and recovery: Deadlock detection and recovery is a technique used by operating systems to detect and resolve deadlocks when they occur. This can be achieved through various methods such as monitoring the state of the system, using algorithms to detect when a deadlock has occurred and taking action to resolve the deadlock. Deadlock detection and recovery are considered to be a less effective approach than deadlock prevention, as it can only be used to resolve deadlocks after they have occurred. However, it can be useful in cases where it is not possible or practical to prevent deadlocks altogether.
- Deadlock Ignorance: Deadlock ignorance is a technique used by operating systems where the operating system does not take any steps to prevent, detect or recover from deadlocks. It is based on the assumption that deadlocks will occur infrequently, and that their impact on the system will be minimal. This approach is generally considered to be less effective than deadlock prevention or detection and recovery, as it can lead to poor system performance and potentially cause the system to become unresponsive. It is generally used in systems where the cost of implementing deadlock prevention or detection and recovery mechanisms is greater than the expected cost of deadlocks. However, it is not recommended for systems where deadlocks could lead to serious consequences.
In summary One of the most common ways to avoid deadlocks is to ensure that all shared resources are requested and released in a specific order. This is known as the "two-phase lock" protocol, which requires that a process must request all the resources it needs before it begins execution and release all resources before it completes. Another approach is to use a timeout-based mechanism, which allows a process to wait for a resource to become available for a certain amount of time before giving up and trying again later.
Deadlocks are a significant problem in operating systems and distributed systems, and various methods have been proposed to prevent and detect them. Deadlock prevention is the best approach as it eliminates the possibility of deadlocks altogether, but this is not always possible or practical. Deadlock detection and recovery is the next best option, which is used to detect and recover from deadlocks when they do occur.
Advantages of Deadlock in Operating System
- Deadlock can be used to prevent low-priority processes from hogging system resources.
- Deadlock can be used to prevent processes from accessing resources that they are not authorized to access.
- Deadlock can be used to prevent processes from accessing resources that are in use by other processes.
Disadvantages of Deadlock in Operating System
- Deadlock can cause a system to become unresponsive, resulting in poor system performance.
- Deadlock can lead to wasted system resources as processes are stuck waiting for resources that they can never acquire.
- Deadlock can cause processes to become stuck in an infinite loop, which can cause the system to crash.
- Deadlock can be difficult to detect and resolve, which can make it hard to troubleshoot and fix problems.
- Deadlock can be costly to implement, as it requires additional resources and programming to prevent, detect and recover from deadlocks.
- Deadlock prevention and detection mechanisms can also introduce additional overheads and complexity to the system, which can affect its overall performance.
Difference between Starvation and Deadlock
Many a times deadlock and starvation are considered same but they are not same they are different from each other the key difference between them include:
| Deadlock | Starvation |
|---|---|
| Deadlock is a situation where two or more processes are unable to proceed because each is waiting for one of the others to release resource | starvation is a situation where a process is unable to acquire the resources it needs to continue execution. |
| Deadlock is caused by a circular wait, where each process is waiting for a resource held by the next process in the chain | starvation is caused by a lack of resources or by a system that is unable to allocate resources fairly. |
| Deadlock results in all processes involved being stuck and unable to make progress | starvation results in a single process being unable to make progress. |
| Deadlock is a state where the processes are blocked and unable to move forward | starvation is a state where a process is not getting the resources it needs to make progress. |
| Deadlock detection and recovery mechanisms are used to detect and resolve deadlocks | starvation prevention mechanisms are used to ensure that resources are allocated fairly and that no process is left waiting indefinitely |
| Deadlock is a problem that occurs in operating systems and distributed systems | starvation can occur in any system where resources are shared among multiple processes. |
Conclusion
In the above article, we have discussed the deadlock in os followed by the proper definition and what is a deadlock, and the conditions for deadlock in os to occur we have discussed them in detail followed by the method to avoid or handle deadlock in the operating system with all the methods in detail followed by advantages and disadvantages of deadlock in the operating system and ended with a difference between starvation and deadlock in os.