aio-libs / multidict / 38229223837

86%

Build Type

push

github

Committed by web-flow

Commit Message

Read getall() lock-free for a table without repeated keys (#1776)

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## What do these changes do?

On the free-threaded build, `getall()` of a multidict whose table has
never held a repeated key now takes the same lock-free path as `get()`:
at most one entry can match, so it is the same lookup, wrapped in a
one-item list. A race falls back to the critical section, as `get()`
does. A table with repeated keys still walks under the lock.

The `maybe_dups` flag that tells the two cases apart is set in place on
a live table by inserts and by `extend()`, so it is now read and written
through relaxed atomics (`htkeys_maybe_dups()`,
`htkeys_set_maybe_dups()`). A stale read is harmless: it only makes
`getall()` return the first match, as if it ran before the insert that
added the second one. The lock-free lookup is factored out of `get()` as
`_md_lockfree_get()` so both use it.

The GIL build and the pure-Python implementation are unaffected.

## Are there changes in behavior for the user?

No; `getall()` is faster on the free-threaded build.

## Is it a substantial burden for the maintainers to support this?

No. It reuses `get()`'s lock-free lookup and reader protocol.

## Related issue number

N/A

## Checklist

- [x] I think the code is well written
- [x] Unit tests for the changes exist
- [x] Documentation reflects the changes (N/A, no documented behavior
changed)
- [ ] If you provide code modification, please add yourself to
`CONTRIBUTORS.txt` (N/A, this repo has no `CONTRIBUTORS.txt`)
- [x] Add a new news fragment into the `CHANGES/` folder
- [x] `make doc-spelling` passes and any new technical words are added
to `docs/spelling_wordlist.txt`

Drafted with Claude Opus 5.5 (Claude Code); to be reviewed by @asvetlov
before it leaves draft.

<details>
<summary>Agent run details (optional, for reviewers)</summary>

Tests, after rebasing on 3977c660:
- 3.14.7t (free-threaded): 4243 passed, 197 skipped
- 3.14.7 (GIL): 4... (continued)

Coverage Stats

832 of 1664 branches covered (50.0%)

Branch coverage included in aggregate %.

21 of 26 new or added lines in 2 files covered. (80.77%)

2 existing lines in 1 file now uncovered.

9778 of 10667 relevant lines covered (91.67%)

1.83 hits per line