fix: claim state_sync_requested with compare_exchange#3891
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Replace separate load/store when accepting a TxHashSetArchive with an atomic compare_exchange so two concurrent messages cannot both observe the flag as true. Addresses mimblewimble#3588.
wiesche89
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Jul 11, 2026
| // and proceed (load+store race; see #3588). | ||
| if self | ||
| .state_sync_requested | ||
| .compare_exchange(true, false, Ordering::SeqCst, Ordering::Relaxed) |
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Issue #3588 raised a static analysis concern about another thread updating the flag between the load and store. The race described in this PR does not appear reachable, since archive responses from a peer are processed one at a time. Could we clarify which concrete interleaving this fixes? If it is a delayed response overlapping a newer request, this boolean still cannot tell them apart.
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Summary
Fixes #3588.
When handling
TxHashSetArchive, the code used a non-atomic check-then-clear:Two concurrent archive messages could both observe
trueand proceed.Change
Use
compare_exchange(true → false)so only one handler claims the outstanding state-sync request.Test plan
cargo test -p grin_p2p --lib -- --test-threads=1