Deadlocks in Operating Systems

A situation where two or more processes are stuck waiting for each other indefinitely, preventing any further progress.

A finite collection of resources that are shared by processes. They can be individual resources or resource types.

A unique identifier for a type of resource, such as a CPU, a printer, or a file.

The number of instances available for a particular resource type.

The action of a process requesting access to a resource. If the resource is unavailable, the process will typically wait until the resource becomes available.

The action of a process using a resource that it has been granted access to.

The action of a process releasing a resource that it has been using, making it available for other processes.

Only one process can utilize a resource at a time. This condition is essential for preventing data corruption.

A process can hold a resource while it is also waiting for additional resources that are currently held by other processes. This can lead to a deadlock situation because the process is blocked from acquiring the additional resources it needs.

Resources cannot be forcibly taken away from a process (preempted). Resources can only be released voluntarily by the process.

A circular chain of processes exists where each process is waiting for a resource that is held by the next process in the chain. Eventually, the last process is waiting for the first process, creating an unbreakable cycle.

A graphical representation of the resource allocation state in a system. It shows the relationships between processes and resources, including their allocations and requests.

An edge in the resource allocation graph that depicts a process requesting a resource.

An edge in the resource allocation graph that depicts a resource being allocated to a process.

A system state where the allocation of resources is such that all processes can potentially complete their execution without encountering a deadlock, even if some processes need to wait for additional resources.

A system state where the allocation of resources creates a possibility for deadlock, meaning that at least one process may not be able to obtain the resources it requires to complete execution, leading to a standstill.

A set of techniques designed to prevent deadlock by ensuring that at least one of the four necessary conditions for deadlock is never met.

A technique for preventing deadlock by ensuring that all resources needed by a process are allocated to it before the process starts executing. This ensures that the process will not be waiting for additional resources while holding other resources, which is a key condition for deadlock.

A deadlock prevention technique that requires a process to release all resources it currently holds before making any new resource requests. This prevents the hold-and-wait condition, which is a key condition for deadlock.

A deadlock prevention technique that involves forcing a process to release a resource it holds when it needs to request a new resource that is currently unavailable. This ensures that processes do not hold resources while waiting for new ones, preventing the hold-and-wait condition.

A deadlock prevention technique that establishes a total ordering for resource types and requires processes to request resources in increasing order of their assigned numbers. This prevents the circular wait condition, which is a key condition for deadlock.

A set of techniques designed to avoid deadlock by ensuring that the system will always remain in a safe state, preventing the occurrence of a deadlock. It uses information about the current resource allocation and future resource requests to make decisions about resource allocation.

A deadlock avoidance technique that is based on the idea of allocating resources to processes only if granting the request will not result in a deadlock situation. It uses the Banker's algorithm to determine whether a resource request can be granted safely.

A set of techniques designed to detect deadlock situations after they occur and then recover from them. The system attempts to identify deadlock conditions in the system and take action to resolve them.

A graph that represents the dependencies between processes in a system, specifically indicating which processes are waiting for which other processes to release resources. An edge from Ti to Tj in the graph implies that process Ti is waiting for process Tj to release a resource that Ti needs.

A technique for reversing the effects of a deadlock by terminating one or more processes involved in the deadlock. The terminated processes may need to be restarted, potentially restarting the process. It is a drastic step to take.

A deadlock recovery technique that involves forcibly taking away a resource from a process that is holding it. The resource can then be assigned to another process. The process that had its resource confiscated must be rolled back to a safe state and restarted.

A process is rolled back to an earlier safe state to recover from deadlock. The process will have to redo some of its work that was completed before the deadlock occurred.

A potential problem in deadlock recovery using preemption, in which the same process is continuously chosen as the victim, preventing it from making progress and eventually leading to starvation. This requires careful strategies to prevent this issue.