add lock to http linux listener to fix race condition

Author: hohong

Release/src/http/listener/http_linux_server.cpp

@@ -570,15 +570,15 @@ void hostport_listener::stop()
 
 void hostport_listener::add_listener(const std::string& path, http_listener* listener)
 {
-    pplx::extensibility::scoped_read_lock_t lock(m_listeners_lock);
+    pplx::extensibility::scoped_rw_lock_t lock(m_listeners_lock);
 
     if (!m_listeners.insert(std::map<std::string,http_listener*>::value_type(path, listener)).second)
         throw std::invalid_argument("Error: http_listener is already registered for this path");
 }
 
 void hostport_listener::remove_listener(const std::string& path, http_listener*)
 {
-    pplx::extensibility::scoped_read_lock_t lock(m_listeners_lock);
+    pplx::extensibility::scoped_rw_lock_t lock(m_listeners_lock);
 
     if (m_listeners.erase(path) != 1)
         throw std::invalid_argument("Error: no http_listener found for this path");
@@ -652,7 +652,7 @@ pplx::task<void> http_linux_server::register_listener(http_listener* listener)
     auto path = parts.second;
 
     {
-        pplx::extensibility::scoped_read_lock_t lock(m_listeners_lock);
+        pplx::extensibility::scoped_rw_lock_t lock(m_listeners_lock);
         if (m_registered_listeners.find(listener) != m_registered_listeners.end())
             throw std::invalid_argument("listener already registered");
 
@@ -679,29 +679,32 @@ pplx::task<void> http_linux_server::unregister_listener(http_listener* listener)
     auto parts = canonical_parts(listener->uri());
     auto hostport = parts.first;
     auto path = parts.second;
-    // First remove listener registration.
-    std::unique_ptr<pplx::extensibility::reader_writer_lock_t> pListenerLock;
-    {
-        pplx::extensibility::scoped_read_lock_t lock(m_listeners_lock);
-        {
-            auto hostport_listeners = m_listeners.find(hostport);
-            if (hostport_listeners == m_listeners.end())
-            {
-                throw std::invalid_argument("Error: no listener registered for that host");
-            }
-
-            hostport_listeners->second->remove_listener(path, listener);
-
-        }
+	// First remove the listener from hostport listener
+    {
+		pplx::extensibility::scoped_read_lock_t lock(m_listeners_lock);
+		auto itr = m_listeners.find(hostport);
+		if (itr == m_listeners.end())
+		{
+			throw std::invalid_argument("Error: no listener registered for that host");
+		}
+
+		itr->second->remove_listener(path, listener);
+	}
+
+	// Second remove the listener form listener collection
+    std::unique_ptr<pplx::extensibility::reader_writer_lock_t> pListenerLock = nullptr;
+	{
+        pplx::extensibility::scoped_rw_lock_t lock(m_listeners_lock);
         pListenerLock = std::move(m_registered_listeners[listener]);
         m_registered_listeners[listener] = nullptr;
         m_registered_listeners.erase(listener);
     }
 
     // Then take the listener write lock to make sure there are no calls into the listener's
     // request handler.
+	if (pListenerLock != nullptr)
     {
-        pplx::extensibility::scoped_read_lock_t lock(*pListenerLock);
+        pplx::extensibility::scoped_rw_lock_t lock(*pListenerLock);
     }
 
     return pplx::task_from_result();