Fix mutex deadlock around app button subscriptionsfix/fix_button_subscriptions_mutex_deadlock

Sometimes there was observed mutex deadlock while
more then one thread are accessing buttons subscriptions
container protected with data accessor class. The
issue is happening when one thread is trying to
unregister application, acquires applications lock and
trying to save application resumption data which at
some point requires app subscribed buttons lock to
be acquired. At the same moment another thread is
trying to resume application data and acquires
subscribed buttons accessor after which is trying
to send notifications to HMI, which at some point
requires applications lock to be acquired. When these
two threads have a time intersection, mutex deadlock
is happening.
To resolve this deadlock, button subscription accessor
has been replaced with temporary accessor + copying
protected content to a local variable which allows to
release that lock beforehand.

2 files changed, 12 insertions, 10 deletions

diff --git a/src/components/application_manager/src/message_helper/message_helper.cc b/src/components/application_manager/src/message_helper/message_helper.cc
index d6fbed115b..2afecf037a 100644
--- a/src/components/application_manager/src/message_helper/message_helper.cc
+++ b/src/components/application_manager/src/message_helper/message_helper.cc
@@ -1108,8 +1108,7 @@ void MessageHelper::SendAllOnButtonSubscriptionNotificationsForApp(
     return;
   }
 
-  DataAccessor<ButtonSubscriptions> button_accessor = app->SubscribedButtons();
-  ButtonSubscriptions subscriptions = button_accessor.GetData();
+  const ButtonSubscriptions subscriptions = app->SubscribedButtons().GetData();
   ButtonSubscriptions::iterator it = subscriptions.begin();
   for (; subscriptions.end() != it; ++it) {
     SendOnButtonSubscriptionNotification(
diff --git a/src/components/application_manager/src/resumption/resumption_data.cc b/src/components/application_manager/src/resumption/resumption_data.cc
index 9046fe35ad..0312975fec 100644
--- a/src/components/application_manager/src/resumption/resumption_data.cc
+++ b/src/components/application_manager/src/resumption/resumption_data.cc
@@ -148,20 +148,23 @@ smart_objects::SmartObject ResumptionData::GetApplicationSubscriptions(
   }
   LOG4CXX_DEBUG(logger_, "app_id:" << application->app_id());
 
-  DataAccessor<ButtonSubscriptions> button_accessor =
-      application->SubscribedButtons();
+  {
+    DataAccessor<ButtonSubscriptions> button_accessor =
+        application->SubscribedButtons();
 
-  const ButtonSubscriptions& button_subscriptions = button_accessor.GetData();
+    const ButtonSubscriptions& button_subscriptions = button_accessor.GetData();
 
-  LOG4CXX_DEBUG(logger_, "SubscribedButtons:" << button_subscriptions.size());
-  Append(button_subscriptions.begin(),
-         button_subscriptions.end(),
-         strings::application_buttons,
-         subscriptions);
+    LOG4CXX_DEBUG(logger_, "SubscribedButtons:" << button_subscriptions.size());
+    Append(button_subscriptions.begin(),
+           button_subscriptions.end(),
+           strings::application_buttons,
+           subscriptions);
+  }
 
   for (auto extension : application->Extensions()) {
     extension->SaveResumptionData(subscriptions);
   }
+
   return subscriptions;
 }