BlockedEvent

BlockedEvent is a synchronization primitive in concurrent programming designed to block progress until a condition is satisfied. It represents an event that is initially blocked and becomes signaled when a trigger occurs, allowing waiting threads or tasks to continue. Unlike a permanently set event, a BlockedEvent can be reset to the blocked state after release, enabling reuse in repetitive workflows. Typical operations include wait (with optional timeout), set or signal to release waiters, and reset to block again. In many implementations, a BlockedEvent is built on lower‑level primitives such as mutexes and condition variables or semaphores, and can be integrated with asynchronous runtimes.

Usage scenarios include initialization barriers, gating access to resources that require preconditions, and coordinating asynchronous work that must not proceed until dependencies are resolved. Designers should consider potential issues such as deadlocks, missed wakeups, and the need for cancellation or timeout handling. Proper use often involves ensuring that every wait has a corresponding signal and that reset semantics are well-defined to avoid confusing reuse.

Although not a universal term, the concept appears in various frameworks under different names, such as gated events, blocking events, or conditional synchronization primitives. See also: Event, Condition variable, Semaphore, Barrier.