Aias00 opened a new pull request, #3519:
URL: https://github.com/apache/dubbo-go/pull/3519
## What
`ServiceMappingChangedListenerImpl.Stop` writes the `stop` field **without**
`lstn.mux`, while `OnEvent` reads `stop` **under** `lstn.mux`. The unlocked
write races `OnEvent` (data race on the `int` field) and lets a mapping event
be processed after the listener has been stopped.
## Why
```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
...
}
func (lstn *ServiceMappingChangedListenerImpl) Stop() {
lstn.stop = ServiceMappingListenerStop // write WITHOUT
mux
}
```
`Stop` is reached from `serviceDiscoveryRegistry.stopListen` (under the
registry's `s.lock`, not `lstn.mux`), so a concurrent `UnSubscribe` and a
`ServiceMappingChangedEvent` delivered to `OnEvent` race on `stop`. `go test
-race` flags it.
## Fix
Acquire `lstn.mux` in `Stop` before writing `stop`. `Stop` is not called
re-entrantly from `OnEvent`'s held-`mux` call stack (it is reached via
`UnSubscribe`/`stopListen`, independent of the `OnEvent` → `SubscribeURL`
path), so there is no self-deadlock.
## Tests
Added `TestServiceMappingChangedListener_StopRace`: 100 rounds of concurrent
`Stop()` vs `OnEvent(nil)` (which acquires `mux`, reads `stop`, early-returns),
passing under `-race`.
Fixes #3518
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