ListenWebTransport ran wt.Serve on a goroutine per socket and returned a stop
func calling wt.Close. Serve takes a reference on the server's refCount
WaitGroup and Close waits on it, so the pair breaks the WaitGroup's own rule
that an Add starting from zero must happen before a Wait. The race detector
models that rule as a read of wg.sema in Add against a write in Wait, and
reports it whenever Wait observes a non-zero counter: a listener stopped
before its serve goroutine has run at all, which is every test that builds a
stack and tears it down without a worker connecting. sync is compiled without
instrumentation, so the report names the two ListenWebTransport call sites
with no frame in between. webtransport-go v0.13.0 carries the same code.
The accept loop moves here. quic.ListenEarly builds the listener Serve would
have built, with the datagram and partial-delivery options the session layer
requires, and each connection goes to Server.ServeQUICConn, which touches no
part of that WaitGroup. The stop func keeps the order Close established:
Close first, so every CONNECTION_CLOSE frame is transmitted while the sockets
are still open, then the accept loops are cancelled and drained, then the
listeners and sockets close.
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
