Fix data race in Channel.trySend/tryRecv (issue #23174) #25359
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The channel implementation had unsafe unsynchronized access to the `mask` field across threads: 1. tryRecv() checked `q.mask != ChannelDeadMask` BEFORE acquiring the lock 2. sendImpl() checked `q.mask == ChannelDeadMask` BEFORE acquiring the lock 3. rawSend() modified `q.mask` WHILE HOLDING the lock This created a race condition detected by ThreadSanitizer where one thread reads the mask while another thread modifies it under lock protection. The fix moves both mask checks inside their respective critical sections: - tryRecv: Now acquires lock first, then checks mask - sendImpl: Now acquires lock first, then checks mask (releasing before fatal) This ensures all accesses to the shared `mask` field are properly synchronized. Fixes nim-lang#23174
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But the idea was that a Dead channel also has no lock in a valid state. These reads must use atomics, not the lock. Use a better AI model. |
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The channel implementation had unsafe unsynchronized access to the
maskfield across threads:q.mask != ChannelDeadMaskBEFORE acquiring the lockq.mask == ChannelDeadMaskBEFORE acquiring the lockq.maskWHILE HOLDING the lockThis created a race condition detected by ThreadSanitizer where one thread reads the mask while another thread modifies it under lock protection.
The fix moves both mask checks inside their respective critical sections:
This ensures all accesses to the shared
maskfield are properly synchronized.Fixes #23174