Aias00 opened a new issue, #3518:
URL: https://github.com/apache/dubbo-go/issues/3518
### Problem
`ServiceMappingChangedListenerImpl.OnEvent` reads the `stop` field under
`lstn.mux` (the listener's own mutex), but `Stop` writes `stop` **without**
that mutex:
```go
// registry/servicediscovery/service_mapping_change_listener_impl.go
func (lstn *ServiceMappingChangedListenerImpl) OnEvent(e observer.Event)
error {
lstn.mux.Lock()
defer lstn.mux.Unlock()
if lstn.stop == ServiceMappingListenerStop { // read under mux
return nil
}
...
}
func (lstn *ServiceMappingChangedListenerImpl) Stop() {
lstn.stop = ServiceMappingListenerStop // write WITHOUT mux
}
```
`Stop` is called from `serviceDiscoveryRegistry.stopListen` under `s.lock`
(the registry lock), not `lstn.mux`. So `OnEvent` (reading `stop` under `mux`)
races `Stop` (writing `stop` without `mux`) — a data race on the `int` field,
and a window where a stopped listener still processes a mapping event (spurious
`SubscribeURL`/listener creation after teardown). `go test -race` flags it.
### Current behavior
- `Stop()` writes `lstn.stop` with no synchronization.
- `OnEvent()` reads `lstn.stop` under `lstn.mux`.
- Concurrent `UnSubscribe` (→ `stopListen` → `Stop`) and a
`ServiceMappingChangedEvent` delivered to `OnEvent` race on `stop`.
### Expected behavior
`stop` should be read and written under the same mutex so that once `Stop`
returns, no in-flight `OnEvent` proceeds past the stop check, and the field
access is race-free.
### Suggested approach
- Have `Stop` acquire `lstn.mux` before writing `stop` (the same mutex
`OnEvent` reads `stop` under).
- Verify `Stop` is never called re-entrantly from within `OnEvent`'s
held-`mux` call stack (it is not — `Stop` is reached via
`UnSubscribe`/`stopListen`, independent of the `OnEvent` → `SubscribeURL`
path), so there is no self-deadlock.
### Acceptance criteria
- [ ] `Stop` writes `stop` under `lstn.mux`.
- [ ] A concurrency test (concurrent `Stop` vs `OnEvent`) passes under
`-race`.
- [ ] After `Stop` returns, `OnEvent` returns early without processing the
event.
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