explain lack of finalizer ordering in godoc

Author: deads2k

staging/src/k8s.io/apimachinery/pkg/apis/meta/v1/types.go

@@ -250,6 +250,15 @@ type ObjectMeta struct {
 	// is an identifier for the responsible component that will remove the entry
 	// from the list. If the deletionTimestamp of the object is non-nil, entries
 	// in this list can only be removed.
+	// Finalizers may be processed and removed in any order.  Order is NOT enforced
+	// because it introduces significant risk of stuck finalizers.
+	// finalizers is a shared field, any actor with permission can reorder it.
+	// If the finalizer list is processed in order, then this can lead to a situation
+	// in which the component responsible for the first finalizer in the list is
+	// waiting for a signal (field value, external system, or other) produced by a
+	// component responsible for a finalizer later in the list, resulting in a deadlock.
+	// Without enforced ordering finalizers are free to order amongst themselves and
+	// are not vulnerable to ordering changes in the list.
 	// +optional
 	// +patchStrategy=merge
 	Finalizers []string `json:"finalizers,omitempty" patchStrategy:"merge" protobuf:"bytes,14,rep,name=finalizers"`