1. What is Deadlock in OS?
Deadlock in OS is a scenario in operating systems where two or more processes are unable to proceed because each process is waiting for a resource that is being held by another process. This situation creates a standstill where no progress can be made until the deadlock is resolved. Deadlocks can occur in various systems, including computer networks, distributed systems, and multi-threaded applications.
In a deadlock, each process is stuck in a waiting state, unable to proceed with its execution. This occurs when a process requests a resource held by another process, which is waiting for a resource held by the first process. The result is a deadlock cycle, where the processes are stuck in a circular dependency, waiting indefinitely for the resources they need to continue.
Deadlocks can have severe consequences, leading to system crashes, frozen applications, and unresponsive user interfaces. Therefore, it is crucial to understand the causes of deadlock and implement strategies to prevent and handle them effectively.
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2. Necessary Conditions for Deadlock in OS
Deadlocks occur due to the fulfillment of four necessary conditions for deadlock in operating system known as the Coffman conditions. Let's explore each of these conditions in detail:
Mutual Exclusion
The mutual exclusion condition states that some resources can only be accessed by one process at a time. This means that once a process acquires a resource, other processes are denied access until it is released. For example, in a multi-threaded application, a critical section of code may be protected by a lock that can only be held by one thread at a time.
Hold and Wait
The hold and wait condition arises when a process is holding at least one resource and is waiting to acquire additional resources. In this scenario, a process may acquire a resource but cannot proceed with its execution because it requires other resources that are currently held by other processes. This leads to a situation where processes are stuck, waiting for resources to be released.
No Preemption
The no preemption condition states that resources cannot be forcibly taken away from a process. Once a process acquires a resource, it can only release it voluntarily. This means that a process cannot be interrupted or preempted to free up its resources and allow other processes to use them. Preemption could potentially lead to data corruption and inconsistencies if a process is forcefully interrupted during its execution.
Circular Wait
The circular wait condition occurs when a set of processes is circularly waiting for resources. In other words, each process waits for a resource that another process holds in the set, creating a circular dependency. This circular wait cycle prevents any process from acquiring the necessary resources to continue its execution.
By fulfilling these four conditions simultaneously, a deadlock in OS can occur. It is important to note that all four conditions must be present for a deadlock to happen. If any one of these conditions is not met, a deadlock cannot occur.
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