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An operating system, in general, refers to the consolidated set of software that is present in a computer. When the systems of hardware and software work together, they result in providing the required service to the end consumer. Some examples will be put forward to relate it to the real world and clarify any other queries. The most common examples of operating systems are Microsoft Windows, Apple iOS, Google’s Android OS, Apple MacOS, and Linux OS. There is one common problem faced in the operating system called ‘deadlock’ which disturbs the overall process of it. It is a situation where the computer process is stopped because the given resources are assigned to another process. To learn in detail about deadlock and why it is considered a threat to operating systems, we would recommend you continue reading this write-up.
In the blog from the expert writers at AllAssignmentHelp.com, an extensive idea of what deadlock is in the operating system will be discussed.
What is a Deadlock?
Deadlock is a frequent problem in multiprocessing. It occurs when numerous processes share a specific resource, such as software or a soft lock. The interaction among various processes as well as resources can cause problems known as deadlock. It is a non-deterministic bug that can occur in a parallel system. These kinds of bugs are difficult to check and debug. A deadlock in OS is a condition when every process waits for a resource acquired by other processes.
Deadlock can also be defined as a situation where two computer programs use the same resource of data and share access. During the deadlock situation, these computer programs will hinder each other’s way. Most importantly, access to the shared resource would be denied to both programs during deadlocks.
It is a series of blocked processes holding a resource and waiting to access extra resources assigned to another one. In a situation of deadlock, none of the programs can continue until another program releases resources. Therefore, it becomes difficult for users to continue with their programs. Besides this, it is also annoying when the system hangs frequently.
An Example of Deadlock
A deadlock is a situation where each process is not correctly processed as the resources are used by other processes. Let us give you an example to help you understand this term better. The following are a few examples of deadlock in OS.
- Let’s suppose, for example, that there is a one-way road and two trucks are coming towards each other. On a one-way road, we all know that only one vehicle can pass at a time. In these circumstances, none of the vehicles can pass, as there is a blockage and no space left for them to cross and pass. You can use the same situation to understand the concept of deadlock, where one process needs resources that are already occupied by the other process. This causes distortion and failure.
- If you are not familiar with the term, you can understand it with this example. Consider a situation where three of your friends are asked to work on a group project by your teacher. Topic A is assigned to one friend, Topic B is assigned to a second friend, and Topic C is assigned to a third friend. Here, you all depend on each other and are holding one resource at a time. To make the cycle work, you need to share your work and complete your project on time. In the operating system, the programs could not interchange their resources, and none of the processes were progressing, resulting in a deadlock.
Which Deadlock Resource Process is Used in Operation Systems?
The system has a definite number of resources to be distributed among the processes. Computer processes need various types of resources to complete the execution of activities. However, these resources are approved in systematic order. These include requesting, waiting, and realizing:
- Requesting: Resources are asked for by the processes.
- Waiting: The operating system grants accessible resources. In the case of unavailability of resources as well as demanding resources, the process is required to wait.
- Realizing: The process utilizes the accessible resources and releases them upon completion of the tasks.
If there are no resources available, none of the programs can execute since the release of the resources they need. The requested resources are associated with other programs that are also waiting for resources held by other programs. Now, we shall move forward to the causes of deadlock. Now our experts from Assignment Help will tell you about the causes of deadlocks in the operating system.
Are Starvation and Deadlock the Same?
This is one of the common confusions that occur among students when studying programming subjects, and it is also the reason why they look out for programming language assignments help to submit a well-written assignment on the difference between deadlock and starvation. Let us clarify this term for you.
- Deadlock is a situation where all processes are blocked because they do not get their resources on time. On the other hand, in starvation, low-level processes get blocked and high-level processes are effectively processed.
- There is no immediate solution for deadlock, which is why it is often compared to infinite waiting. while starvation does not have information waiting and can be solved in a short or long period.
- In deadlock, the programming process is blocked as the required resources are occupied or used by other processes at the same time. In starvation, the process is blocked as all the resources are used by high-priority programming processes.
What Causes Deadlock in OS (operating system)?
It is said that deadlock in an operating system arises when the following four conditions hold at the same time in the system:
Mutual Exclusion
At least one or more of the allocated resources are not shareable. Each resource is assigned to only one process at a time. If any other process demands the same resources, the demanding process is required to wait until the executing process releases them. The process of mutual exclusion, or rather, the condition of mutual exclusion, is said to exist in cases of deadlock. This happens when there is a single resource that can be allocated to one program and not more than that.
Hold and Wait
The requesting process already holds a resource and waits for other resources that are currently being used by the other process. Hold and wait is another condition that can lead to a deadlock situation in an operating system. According to this condition, it is provided that a single program can use multiple resources for its functioning. Even after that, it requests resources from other programs. A hypothetical example can be considered. Process P is using Resource 5 and Resource 6. Process Q is using resource 2. Even then, Process P requests Resource 2 from Process Q.
Non-Pre-emption
Resources that are assigned to the other tasks cannot be prompted. Once a resource is held by a process, it cannot be taken away from the active process. The requesting process has to wait until the process of holding this resource releases it willingly. This condition provides that a resource can in no way be preempted from a process. A process and resource will only be detached if the program, by a voluntary measure, lets go of the resources. Hence, a process cannot preempt a resource from another process before it is done with execution. When trying to do so, deadlock arises.
Circular Wait
A circular wait that causes a deadlock is a kind of circular loop. This is generally caused by an interconnected circular chain of processes and resources. Besides this, a series of processes that are waiting for each other in a chain system must exist. Here, each process in the chain waits for the resource detained by another process in the circular chain. This occurs when the first process is waiting to hold the resource that is held by the second process.
On the other hand, the second process also waits to hold the resource that is held by the third process. This continues, depending on the number of processes and their resources. The endpoint of this circular loop lies where the last process waits to hold the resource held by the first process. It sounds a bit confusing, but in a practical scenario, deadlocks can hamper or cause a delay in activities.
Methods of Detecting a Deadlock
We hope that by now you might be clear about what deadlock is in OS. Deadlocks are one of the most common problems that occur in computer systems and require timely detection and prevention. Before looking at the steps for prevention, let us first understand the different methods of detecting a deadlock.
- The first is to check the processes of the computer system and determine whether they are all performing. If there is some issue with the process or if the resources are not timely structured, then it can be assumed that deadlocks are being formed.
- Another method is the resource allocation graph, which will help in determining whether the processes are blocked by other processes or not. This deadlock detection provides a good understanding of the formation of blocks.
- The other potential deadlock formation is through a wait-for-graph, which can check if a cycle exists between those events.
What are the Different Methods for Handling Deadlock in OS?
Since the description and the conditions leading to a situation of deadlock have been described, we will now shed light on the different ways of handling deadlock in an OS. There are mainly three ways to deal with the deadlock in the operating system, and they are:
- Deadlock prevention or avoidance
- Deadlock detection and recovery
- Ignore the problem altogether.
Deadlock prevention and avoidance
The deadlock prevention method is the easiest method for handling deadlock. In this method, deadlock can be prevented by avoiding any one of the four conditions mentioned above. Most importantly, as these four conditions are mandatory, the system can prevent deadlock by eliminating one of them.
Effective measures must be taken so that no transaction between the processes and resources takes place, leading to a deadlock. Besides this, the system evaluates every transaction beforehand. If any possibility of a deadlock is seen, the transaction is seized from the action. For the prevention of deadlocks, time schemes like wait-die schemes and wound-wait schemes are used. The underlying idea behind the occurrence of deadlock is that all the instances of the Coffman condition function at once. Deadlock can be prevented by the simple concept of failing, even under either of these conditions. No matter how easy or simple this may sound, the implementation of this method physically is still debatable. But then again, operators use such an interface to deal with situations of deadlock.
In deadlock avoidance, the OS checks whether the system is in a safe or unsafe state. Most importantly, the avoiding process works until the system comes to a safe state. Besides this, the operating system determines the distribution of resources, ensuring that the resources do not create deadlocks. This approach includes the elimination of the conditions of mutual exclusion, no prompt, hold and wait, and circular wait. We can prompt a resource from one process and provide it to another requesting process. This will not allow the system to go into a deadlock state.
Detection and Recovery from Deadlocks
If the deadlock prevention or avoidance approach fails, detection and recovery from deadlocks is another way to deal with deadlocks. Moreover, deadlock detection is a process used to determine whether a deadlock exists or not. This approach identifies the resources as well as the process causing the deadlocks. The basic thing is to test the distribution of resources. Once the deadlock is detected, you are required to break it. It can be done using various methods, such as eliminating one or more processes waiting in a circular chain. In addition to this, taking away resources from other processes, which are also deadlocks, is used for recovery.
In this mechanism, OS neither neglects nor utilizes any method to avoid or prevent deadlocks. To overcome deadlocks situations, the OS every so often checks the systems regularly. If there is any deadlock available, recovery techniques are used by the operating system to recover the system. The recovery method includes ending the process in deadlocks. After ending all the processes, it again looks for deadlocks. You need to repeat this process until the system becomes deadlock-free.
A deadlock can be easily detected by employing a resource scheduler. The work of a resource scheduler is to track all the resources and processes available in the system. It can track the different resources that are held by different processes. Once the tracking is done and the deadlock is detected, what can be done is that all the processes employed should be terminated, even though that means the loss of complete progress. After that, a few resources can be extracted and allocated to other processes before the deadlock situation is completely resolved.
Ignorance of Deadlocks Altogether
Ignorance of deadlock is an effective way of handling deadlock by avoiding situations that arise. The wait-for-graph technique can be used where the existence of an edge in the graph shows the presence of deadlock. The method of avoiding deadlock involves mainly analyzing the activities in the operating system. At every step, a process is followed to evaluate whether the process is safe or not. Once an unsafe activity is detected, the OS takes a step back to prevent the deadlock.
This is one of the most widely used mechanisms to deal with deadlocks. This method is used by most operating systems, especially for end-user operations. In this method, the OS assumes that there are no deadlocks. It just ignores it; the users have to restart the system in the event of deadlocks. This approach is used when the interval between the occurrences of deadlocks is shorter. The data lost by the occurrence of deadlock is bearable. Thus, this approach believes that deadlock occurs rarely.
The above-listed were the few measured for deadlock prevention in OS (operating system).
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Frequently Asked Questions
| Question 1: Does deadlock occur in DBMS? The problem of deadlocks appears in database management systems where one or more transactions are dependent on each other for the simultaneous release of resources. |
| Question 2: What are the four causes of deadlock in an operating system? Mutual Exclusion, Hold and Wait, Non-Preemption, and Circular Wait are the four common causes that lead to deadlock in the operating system. |