sensors: allow listing policies while disabling

This patch modifies disableTracingPolicy to release the lock to the
collections while unloading a sensor. Before releasing the lock, the state
is changed to UnloadingState.

Signed-off-by: Kornilios Kourtis <kornilios@isovalent.com>

pkg/sensors/collection.go

@@ -21,6 +21,7 @@ const (
 	LoadErrorState
 	ErrorState
 	LoadingState
+	UnloadingState
 )
 
 func (s TracingPolicyState) ToTetragonState() tetragon.TracingPolicyState {
@@ -35,6 +36,8 @@ func (s TracingPolicyState) ToTetragonState() tetragon.TracingPolicyState {
 		return tetragon.TracingPolicyState_TP_STATE_ERROR
 	case LoadingState:
 		return tetragon.TracingPolicyState_TP_STATE_LOADING
+	case UnloadingState:
+		return tetragon.TracingPolicyState_TP_STATE_UNLOADING
 	default:
 		return tetragon.TracingPolicyState_TP_STATE_UNKNOWN
 	}

pkg/sensors/handler.go

@@ -187,7 +187,12 @@ func (h *handler) disableTracingPolicy(op *tracingPolicyDisable) error {
 		return fmt.Errorf("tracing policy %s is not enabled", op.ck)
 	}
 
+	col.state = UnloadingState
+	// unlock so that policyLister can access the collections (read-only) while we are unloading.
+	h.collections.mu.Unlock()
 	err := col.unload()
+	h.collections.mu.Lock()
+
 	if err != nil {
 		// for now, the only way col.unload() can return an error is if the
 		// collection is not currently loaded, which should be impossible