Add mutual exclusion on Agent between xmpp::StateMachine and io::Read…

…erTask.

TCP close event on a session is handled by xmpp::StateMachine task and
reads handled by io::ReaderTask, hence both tasks can be accessing the
same session at the same time and xmpp::StateMachine destroying the session
while io::ReaderTask reading it.

Change-Id: I09fbdf9b9ea6c31fb6072e7e2f8d40510f32dc03
Closes-Bug:1560242

src/vnsw/agent/cmn/agent.cc

@@ -250,6 +250,12 @@ void Agent::SetAgentTaskPolicy() {
     SetTaskPolicyOne("http client", metadata_exclude_list,
                      sizeof(metadata_exclude_list) / sizeof(char *));
 
+    const char *xmpp_state_machine_exclude_list[] = {
+        "io::ReaderTask"
+    };
+    SetTaskPolicyOne("xmpp::StateMachine", xmpp_state_machine_exclude_list,
+                     sizeof(xmpp_state_machine_exclude_list) / sizeof(char *));
+
     const char *agent_init_exclude_list[] = {
         "xmpp::StateMachine",
         "http client",

src/xmpp/xmpp_session.cc

@@ -298,10 +298,6 @@ void XmppSession::OnRead(Buffer buffer) {
                 break;
             }
 
-            //
-            // XXX Connection gone ?
-            //
-            if (!connection_) break;
             connection_->ReceiveMsg(this, xml);
 
         } else {