Processsynkronisering

Processsynkronisering, or process synchronization, is the coordination of multiple processes or threads to ensure correct outcomes when accessing shared resources or coordinating progress. It addresses challenges such as race conditions, where results depend on the unpredictable order of execution, and aims to prevent deadlocks, livelocks, and starvation. Synchronization applies within operating systems, runtime libraries, and distributed systems.

Common synchronization mechanisms include mutexes or locks, which grant exclusive access to a resource; semaphores, which control access by counting permits; and monitors, which combine mutual exclusion with condition variables for signaling. Other techniques include barriers for synchronizing a group of processes, readers-writers locks to optimize concurrent reads with exclusive writes, and various lock-free or wait-free algorithms based on atomic operations. Hardware support, such as test-and-set or compare-and-swap, and memory barriers, underpins the correct ordering of operations on modern CPUs.

In distributed environments, synchronization becomes more complex and often relies on message passing, coordination services, and consensus protocols. Correct synchronization typically requires adhering to properties like mutual exclusion, progress, and bounded waiting to prevent starvation. Designers must consider granularity, contention, and potential deadlocks, employing strategies such as resource ordering, timeouts, or deadlock detection and recovery.

Applications span operating system kernels, database transactions, parallel computing frameworks, and multi-threaded application runtimes. Related topics include race conditions, locking strategies, and synchronization primitives. Properly implemented process synchronization improves correctness and performance but introduces overhead and complexity, making careful design essential.