checklocks: clarify futex bucket contracts - #14298
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r? @EtiennePerot Could you review PI helper lock requirements and conditional bucket aliases? Focused local Bazel checks passed. Upstream checks have not reported yet. Assisted-by: Codex |
Recognize atomicbitops Racy methods as non-atomic operations. Permit mixed-mode RacyLoad only when all guards are held, and require atomic writes with all guards held exclusively. Distinguish shared-lock reads from lock-free atomic reads so an RLock cannot authorize writes. Check atomic uses of annotated globals at the consuming instruction instead of discarding that instruction. Keep unannotated-global behavior unchanged, preserve function and closure ignores, and distinguish writes to a global from stores of its address. Resolve generic instantiations to their original declarations before classifying atomic operations. This recognizes atomic.Pointer methods without bypassing package or mixed-access checks for generic calls. Assisted-by: Codex
Use atomic.Pointer for the waiter's bucket pointer and require atomic accesses. The generated wrapper only delegates to the same pointer operations, but hides them behind a package the checker does not classify as atomic. Waiters are not serialized, so its generated state hooks are unnecessary. Declare the PI lock and unlock helpers' existing bucket requirements. Preserve the ordered lock handles and explain why logical bucket aliases and moving waiter membership cannot carry uniform mutex annotations. Document that a queued waiter cannot be reused until WaitComplete returns. Keep the lock-and-revalidate protocol, atomic nil publication after notification and reverse-order bucket release. Assisted-by: Codex
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Closing in favor of consolidated #14345. The expanded replacement commits are prepared locally; the replacement branch has not been pushed yet. Assisted-by: Codex |
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The PI lock and unlock helpers operate on a bucket acquired by their callers. Declare those entry requirements without changing lock scope.
Correct the ordered bucket return contract: the first handle is always non-nil, and the second is nil only when both keys select the same bucket. Retain prose for these conditional aliases that checklocks cannot express.
Include PI waits in waiter lifecycle documentation and state the membership and lock requirements for wake and requeue helpers. Preserve the lock-and-revalidate protocol and reverse-order release.
Assisted-by: Codex