fix(bbr): add read lock to GetBaseModel to prevent concurrent map crash (#2570)

- `GetBaseModel()` reads `loraAdapterToBaseModel` and `baseModels` maps without
  holding a lock, while `ConfigMapUpdateOrAddIfNotExist()` and `ConfigMapDelete()`
  write to these maps under `ds.lock.Lock()`. In Go, concurrent map read and write
  causes `fatal error: concurrent map read and map write`, which crashes the
  process and cannot be recovered.
- Add `ds.lock.RLock()`/`RUnlock()` to `GetBaseModel()` to ensure safe concurrent
  access.
- Add a concurrent read/write test to prevent regression.
- go test -race ./pkg/bbr/datastore/... test passed.

Author: gyliu513

pkg/bbr/datastore/datastore.go

@@ -128,6 +128,8 @@ func (ds *datastore) ConfigMapDelete(configmap *corev1.ConfigMap) {
 
 func (ds *datastore) GetBaseModel(modelName string) string {
 	trimmedModelName := strings.TrimSpace(modelName)
+	ds.lock.RLock()
+	defer ds.lock.RUnlock()
 	// if the given model name is a LoRA adapter, we should return its base model
 	if baseModel, ok := ds.loraAdapterToBaseModel[trimmedModelName]; ok {
 		return baseModel

pkg/bbr/datastore/datastore_test.go

@@ -191,6 +191,21 @@ func TestConfigMapDelete_MissingBaseModel(t *testing.T) {
 	}
 }
 
+func TestGetBaseModel_ConcurrentRace(t *testing.T) {
+	ds := NewDatastore()
+	cm := makeConfigMap(cmName, baseModel, "- a1\n")
+
+	go func() {
+		for i := 0; i < 10000; i++ {
+			_ = ds.ConfigMapUpdateOrAddIfNotExist(cm)
+		}
+	}()
+
+	for i := 0; i < 10000; i++ {
+		ds.GetBaseModel("a1")
+	}
+}
+
 func TestConfigMapDelete_BaseModelCount(t *testing.T) {
 	ds := NewDatastore()
 	cm1 := makeConfigMap(cmName, baseModel, "- a1\n")