stream

Mutual-exclusion lock used by stats whose update logic spans multiple cells or multiple steps and therefore can't be made elementwise atomic. Obtain one for a given Concurrency level via Concurrency.lock: a no-op under Concurrency.None (single-threaded, zero overhead), a platform mutex otherwise.

The lock for a Concurrency level: NoopMutex under Concurrency.None — a single-threaded owner pays no synchronization — and a PlatformMutex under any concurrent level. The same contract the per-stat serializedLock uses, exposed for callers that need a coherent lock for their own coupled state.