async: add shared_awaitable<T> — multi-consumer broadcast awaitable (…#325
Merged
Conversation
…folly::SharedPromise replacement) value_awaitable resumes one waiter and moves its result out (single-shot); shared_awaitable resumes ALL installed waiters and hands each a copy (broadcast), so T must be copyable. It is the coroutine-native replacement for folly::SharedPromise<T> — the pattern where several callers await one in-flight completion (e.g. N threads triggering one checkpoint flush). Single-mutex handshake, resumes performed outside the lock so a resumed coroutine may re-enter; no lost wakeup on the await_suspend/complete race; idempotent complete(). Header-only, stdexec-free. test_shared_awaitable covers both completion orderings, the broadcast (N waiters, one complete), idempotent second complete, copyable-payload sharing, refcounted-state survival, and a TSAN-friendly cross-thread broadcast race (1000 iters x 4 waiter threads + completer). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
…folly::SharedPromise replacement)
value_awaitable resumes one waiter and moves its result out (single-shot); shared_awaitable resumes ALL installed waiters and hands each a copy (broadcast), so T must be copyable. It is the coroutine-native replacement for folly::SharedPromise — the pattern where several callers await one in-flight completion (e.g. N threads triggering one checkpoint flush). Single-mutex handshake, resumes performed outside the lock so a resumed coroutine may re-enter; no lost wakeup on the await_suspend/complete race; idempotent complete().
Header-only, stdexec-free. test_shared_awaitable covers both completion orderings, the broadcast (N waiters, one complete), idempotent second complete, copyable-payload sharing, refcounted-state survival, and a TSAN-friendly cross-thread broadcast race (1000 iters x 4 waiter threads + completer).