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replace the lock in `exec::__nest_rcvr::__complete` with a CAS loop

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
38/100
Issue type
Refactor
Clarity
Mostly clear
Activity status
Stale
Tech stack
cpp
Domain
performance

Research direction

Start with async_scope::spawn and start_detached, then inspect the linked-list notification logic in split. Locate the locking and unlocking in exec::__next_rcvr::__complete (or the __nest_rcvr::__complete named in the title) and compare it with split’s compare-and-swap loop. Done means the completion path uses the CAS-based approach without changing notification behavior or async_scope correctness.

Written by the indexing model from the issue text.

Description

enhancement P1

async_scope::spawn is much slower than start_detached, and I suspect the issue is the locking and unlocking going on in exec::__next_rcvr::__complete. There is similar logic for walking a linked list and notifying each element in the implementation of split, but there it is done more efficiently with a compare-and-swap loop. Maybe the two can share logic.

Dominant language
C++
Stars
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Forks
270
Avg merge
2d 17h
Merged PRs (30d)
37

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