init: clean up DelayService()

ServiceList's services_update_finished flag was overlapped with the
global flag: is_default_mount_namespace_ready. Now DelayService() relies
on the is_default_mount_namespace_ready flag.

Add a service description with 'updatable' flag and invoke 'start
<name>' in 'on init' block (which comes before APEX activation).
See the log for "Cannot start an updatable service".

Bug: 293535323
Test: see the comment
Change-Id: I9341ba1a95d9b3b7c6081b530850d61f105f0a56

init/builtins.cpp

@@ -1304,8 +1304,7 @@ static Result<void> do_perform_apex_config(const BuiltinArguments& args) {
     }
 
     if (!bootstrap) {
-        // Now start delayed services
-        ServiceList::GetInstance().MarkServicesUpdate();
+        ServiceList::GetInstance().StartDelayedServices();
     }
     return {};
 }

init/service.cpp

@@ -420,7 +420,7 @@ Result<void> Service::ExecStart() {
         }
     });
 
-    if (is_updatable() && !ServiceList::GetInstance().IsServicesUpdated()) {
+    if (is_updatable() && !IsDefaultMountNamespaceReady()) {
         // Don't delay the service for ExecStart() as the semantic is that
         // the caller might depend on the side effect of the execution.
         return Error() << "Cannot start an updatable service '" << name_
@@ -581,7 +581,7 @@ Result<void> Service::Start() {
         }
     });
 
-    if (is_updatable() && !ServiceList::GetInstance().IsServicesUpdated()) {
+    if (is_updatable() && !IsDefaultMountNamespaceReady()) {
         ServiceList::GetInstance().DelayService(*this);
         return Error() << "Cannot start an updatable service '" << name_
                        << "' before configs from APEXes are all loaded. "

init/service_list.cpp

@@ -76,10 +76,7 @@ bool ServiceList::IsPostData() {
     return post_data_;
 }
 
-void ServiceList::MarkServicesUpdate() {
-    services_update_finished_ = true;
-
-    // start the delayed services
+void ServiceList::StartDelayedServices() {
     for (const auto& name : delayed_service_names_) {
         Service* service = FindService(name);
         if (service == nullptr) {
@@ -94,7 +91,7 @@ void ServiceList::MarkServicesUpdate() {
 }
 
 void ServiceList::DelayService(const Service& service) {
-    if (services_update_finished_) {
+    if (IsDefaultMountNamespaceReady()) {
         LOG(ERROR) << "Cannot delay the start of service '" << service.name()
                    << "' because all services are already updated. Ignoring.";
         return;

init/service_list.h

@@ -85,14 +85,10 @@ class ServiceList {
 
     void MarkPostData();
     bool IsPostData();
-    void MarkServicesUpdate();
-    bool IsServicesUpdated() const { return services_update_finished_; }
     void DelayService(const Service& service);
+    void StartDelayedServices();
 
-    void ResetState() {
-        post_data_ = false;
-        services_update_finished_ = false;
-    }
+    void ResetState() { post_data_ = false; }
 
     auto size() const { return services_.size(); }
 
@@ -100,7 +96,6 @@ class ServiceList {
     std::vector<std::unique_ptr<Service>> services_;
 
     bool post_data_ = false;
-    bool services_update_finished_ = false;
     std::vector<std::string> delayed_service_names_;
 };