dødlåse

Dødlåse, often translated as deadlock in English, refers to a situation where two or more processes or threads are unable to proceed because each is waiting for the other to release a resource. This creates a circular dependency, effectively halting progress for all involved entities.

In computing, a deadlock typically occurs when four conditions, known as the Coffman conditions, are met simultaneously. These are mutual exclusion, where at least one resource is non-sharable; hold and wait, where a process holds at least one resource and is waiting to acquire additional resources held by other processes; no preemption, where resources cannot be forcibly taken from a process; and circular wait, where a set of processes are waiting for each other in a circular fashion.

Deadlocks can manifest in various scenarios, from operating system resource allocation to database transactions and multi-threaded programming. When a deadlock occurs, the affected processes or threads remain in a suspended state indefinitely unless a deadlock resolution mechanism is employed.

Strategies to handle deadlocks include prevention, avoidance, detection, and recovery. Prevention involves designing systems such that at least one of the Coffman conditions can never occur. Avoidance uses algorithms to ensure that the system never enters an unsafe state where a deadlock might occur. Detection involves periodically checking for deadlocks and then employing recovery techniques if one is found. Recovery typically involves terminating one or more of the deadlocked processes or preempting resources.