Move ProxyConfigService construction onto the IO thread.

net/proxy/proxy_config_service_linux.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_PROXY_PROXY_CONFIG_SERVICE_LINUX_H_
 #define NET_PROXY_PROXY_CONFIG_SERVICE_LINUX_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 121 matching lines @@
     virtual bool BypassListIsReversed() = 0;
 
     // Returns true if the bypass rules should be interpreted as
     // suffix-matching rules.
     virtual bool MatchHostsUsingSuffixMatching() = 0;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(SettingGetter);
   };
 
-  // ProxyConfigServiceLinux is created on the UI thread, and
-  // SetUpAndFetchInitialConfig() is immediately called to synchronously
-  // fetch the original configuration and set up change notifications on
-  // the UI thread.
+  // ProxyConfigServiceLinux is created on the IO thread, and begins
+  // asynchronously on the UI thread fetching the original configuration
+  // and setting up change notifications.
   //
   // Past that point, it is accessed periodically through the
   // ProxyConfigService interface (GetLatestProxyConfig, AddObserver,
   // RemoveObserver) from the IO thread.
   //
   // Setting change notification callbacks can occur at any time and are
   // run on either the UI thread (gconf/gsettings) or the file thread
   // (KDE). The new settings are fetched on that thread, and the resulting
   // proxy config is posted to the IO thread through
   // Delegate::SetNewProxyConfig(). We then notify observers on the IO
   // thread of the configuration change.
   //
-  // ProxyConfigServiceLinux is deleted from the IO thread.
+  // ProxyConfigServiceLinux is deleted from the IO thread but may require
+  // prior shutdown performed on other threads via StartTearDown().
+  // This prior shutdown safely stops change notifications.
   //
   // The substance of the ProxyConfigServiceLinux implementation is
-  // wrapped in the Delegate ref counted class. On deleting the
-  // ProxyConfigServiceLinux, Delegate::OnDestroy() is posted to either
-  // the UI thread (gconf/gsettings) or the file thread (KDE) where change
-  // notifications will be safely stopped before releasing Delegate.
+  // wrapped in the Delegate ref counted class. Destruction of the Delegate
+  // is commenced by StartTearDown() which calls Delegate::OnDestroy() on
+  // the UI thread (gconf/gsettings) or posts it to the file thread (KDE) where
+  // change notifications will be safely stopped before releasing Delegate.
 
   class Delegate : public base::RefCountedThreadSafe<Delegate> {
    public:
     // Constructor receives env var getter implementation to use, and
     // takes ownership of it. This is the normal constructor.
     explicit Delegate(base::Environment* env_var_getter);
     // Constructor receives setting and env var getter implementations
     // to use, and takes ownership of them. Used for testing.
     Delegate(base::Environment* env_var_getter, SettingGetter* setting_getter);
 
-    // Synchronously obtains the proxy configuration. If gconf,
-    // gsettings, or kioslaverc are used, also enables notifications for
-    // setting changes. gconf/gsettings must only be accessed from the
-    // thread running the default glib main loop, and so this method
-    // must be called from the UI thread. The message loop for the IO
-    // thread is specified so that notifications can post tasks to it
-    // (and for assertions). The message loop for the file thread is
-    // used to read any files needed to determine proxy settings.
+    // Posts SetUpAndFetchInitialConfigOnUIThread() to UI thread.  Called
+    // from the IO thread.
     void SetUpAndFetchInitialConfig(
         base::SingleThreadTaskRunner* glib_thread_task_runner,
         base::SingleThreadTaskRunner* io_thread_task_runner,
         MessageLoopForIO* file_loop);
 
     // Handler for setting change notifications: fetches a new proxy
     // configuration from settings, and if this config is different
     // than what we had before, posts a task to have it stored in
     // cached_config_.
     // Left public for simplicity.
     void OnCheckProxyConfigSettings();
 
     // Called from IO thread.
     void AddObserver(Observer* observer);
     void RemoveObserver(Observer* observer);
     ProxyConfigService::ConfigAvailability GetLatestProxyConfig(
         ProxyConfig* config);
 
     // Posts a call to OnDestroy() to the UI or FILE thread, depending on the
-    // setting getter in use. Called from ProxyConfigServiceLinux's destructor.
+    // setting getter in use. Called from
+    // ProxyConfigServiceLinux::StartTearDown().
     void PostDestroyTask();
     // Safely stops change notifications. Posted to either the UI or FILE
     // thread, depending on the setting getter in use.
     void OnDestroy();
 
    private:
     friend class base::RefCountedThreadSafe<Delegate>;
 
     ~Delegate();
 
+    // Synchronously obtains the proxy configuration. If gconf,
+    // gsettings, or kioslaverc are used, also enables notifications for
+    // setting changes. gconf/gsettings must only be accessed from the
+    // thread running the default glib main loop, and so this method
+    // must be called from the UI thread.

[digit1, 2012/10/19 10:32:46]

On the other hand, this comment is probably perfectly fine and informative :)

+    void SetUpAndFetchInitialConfigOnUIThread(
+        MessageLoopForIO* file_loop);
+
     // Obtains an environment variable's value. Parses a proxy server
     // specification from it and puts it in result. Returns true if the
     // requested variable is defined and the value valid.
     bool GetProxyFromEnvVarForScheme(const char* variable,
                                      ProxyServer::Scheme scheme,
                                      ProxyServer* result_server);
     // As above but with scheme set to HTTP, for convenience.
     bool GetProxyFromEnvVar(const char* variable, ProxyServer* result_server);
     // Fills proxy config from environment variables. Returns true if
     // variables were found and the configuration is valid.
@@ skipping 11 matching lines @@
     // This method is posted from the UI thread to the IO thread to
     // carry the new config information.
     void SetNewProxyConfig(const ProxyConfig& new_config);
 
     // This method is run on the getter's notification thread.
     void SetUpNotifications();
 
     scoped_ptr<base::Environment> env_var_getter_;
     scoped_ptr<SettingGetter> setting_getter_;
 
+    // Has initialization completed and it's safe to read cached_config_.
+    bool finished_initialization_;
+
     // Cached proxy configuration, to be returned by
-    // GetLatestProxyConfig. Initially populated from the UI thread, but
-    // afterwards only accessed from the IO thread.
+    // GetLatestProxyConfig. Only accessed from the IO thread.
     ProxyConfig cached_config_;
 
     // A copy kept on the UI thread of the last seen proxy config, so as
     // to avoid posting a call to SetNewProxyConfig when we get a
     // notification but the config has not actually changed.
     ProxyConfig reference_config_;
 
     // The task runner for the glib thread, aka main browser thread. This thread
     // is where we run the glib main loop (see base/message_pump_glib.h). It is
     // the glib default loop in the sense that it runs the glib default context:
     // as in the context where sources are added by g_timeout_add and
     // g_idle_add, and returned by g_main_context_default. gconf uses glib
     // timeouts and idles and possibly other callbacks that will all be
     // dispatched on this thread. Since gconf is not thread safe, any use of
     // gconf must be done on the thread running this loop.
     scoped_refptr<base::SingleThreadTaskRunner> glib_thread_task_runner_;
     // Task runner for the IO thread. GetLatestProxyConfig() is called from
     // the thread running this loop.
     scoped_refptr<base::SingleThreadTaskRunner> io_thread_task_runner_;
 
     ObserverList<Observer> observers_;
 
     DISALLOW_COPY_AND_ASSIGN(Delegate);
   };
 
   // Thin wrapper shell around Delegate.
 
   // Usual constructor
-  ProxyConfigServiceLinux();
+  ProxyConfigServiceLinux(
+      base::SingleThreadTaskRunner* glib_thread_task_runner,
+      base::SingleThreadTaskRunner* io_thread_task_runner,
+      MessageLoopForIO* file_loop);
   // For testing: take alternate setting and env var getter implementations.
   explicit ProxyConfigServiceLinux(base::Environment* env_var_getter);
   ProxyConfigServiceLinux(base::Environment* env_var_getter,
                           SettingGetter* setting_getter);
 
   virtual ~ProxyConfigServiceLinux();
 
+  // This is only public for testing.
   void SetupAndFetchInitialConfig(
       base::SingleThreadTaskRunner* glib_thread_task_runner,
       base::SingleThreadTaskRunner* io_thread_task_runner,
       MessageLoopForIO* file_loop) {
     delegate_->SetUpAndFetchInitialConfig(glib_thread_task_runner,
                                           io_thread_task_runner, file_loop);
   }
   void OnCheckProxyConfigSettings() {
     delegate_->OnCheckProxyConfigSettings();
   }
 
   // ProxyConfigService methods:
   // Called from IO thread.
   virtual void AddObserver(Observer* observer) OVERRIDE;
   virtual void RemoveObserver(Observer* observer) OVERRIDE;
   virtual ProxyConfigService::ConfigAvailability GetLatestProxyConfig(
       ProxyConfig* config) OVERRIDE;
-
+  // Called from Glib thread.
+  virtual void StartTearDown() OVERRIDE;
  private:
   scoped_refptr<Delegate> delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(ProxyConfigServiceLinux);
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_CONFIG_SERVICE_LINUX_H_