`<atomic>`: reconsider atomic wait on `shared_ptr`
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Description
After #3655 fix, atomic wait on shared_ptr has timed backoff for the case of control blocks difference but value match.
We need to consider alternatives to this timed backoff for vNext.
WaitOnAddress on 128 bits may be invented by then.
Otherwise, may consider making atomic<shared_ptr> use a different approach, like the fallback we have for non-lock-free atomics.
vNext note: Resolving this issue will require breaking binary compatibility. We won't be able to accept pull requests for this issue until the vNext branch is available. See #169 for more information.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reading #3655 and the current atomic wait design, then compare the timed backoff with the existing fallback for non-lock-free atomics. Revisit the WaitOnAddress limitation and #169 before vNext work begins; done means a vNext-compatible alternative is selected and implemented without the current binary-compatibility constraint.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- operating-systems, performance
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100