Make the SystemMonitor observer list thread safe.

This is done by using the new observer_list_threadsafe.

Review URL: http://codereview.chromium.org/4288

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@4452 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 43 insertions, 39 deletions

diff --git a/base/system_monitor.h b/base/system_monitor.h
index ec4c593..7a2d4d5 100644
--- a/base/system_monitor.h
+++ b/base/system_monitor.h
@@ -5,13 +5,12 @@
 #ifndef BASE_SYSTEM_MONITOR_H_

 #define BASE_SYSTEM_MONITOR_H_

 

-#include "base/logging.h"

-#include "base/observer_list.h"

+#include "base/observer_list_threadsafe.h"

 #include "base/singleton.h"

 

 namespace base {

 

-// Singleton class for monitoring various system-related subsystems

+// Class for monitoring various system-related subsystems

 // such as power management, network status, etc.

 // TODO(mbelshe):  Add support beyond just power management.

 class SystemMonitor {

@@ -21,25 +20,33 @@ class SystemMonitor {
     return Singleton<SystemMonitor>::get();

   }

 

+  // To start the System Monitor within an application

+  // use this call.

+  static void Start();

+

   //

   // Power-related APIs

   //

 

   // Is the computer currently on battery power.

-  bool BatteryPower() { return battery_in_use_; }

+  // Can be called on any thread.

+  bool BatteryPower() { 

+    // Using a lock here is not necessary for just a bool.

+    return battery_in_use_;

+  }

 

   // Normalized list of power events.

   enum PowerEvent {

-    // The Power status of the system has changed.

-    PowerStateEvent,

-

-    // The system is being suspended.

-    SuspendEvent,

-

-    // The system is being resumed.

-    ResumeEvent

+    POWER_STATE_EVENT,  // The Power status of the system has changed.

+    SUSPEND_EVENT,      // The system is being suspended.

+    RESUME_EVENT        // The system is being resumed.

   };

 

+  // Callbacks will be called on the thread which creates the SystemMonitor.

+  // During the callback, Add/RemoveObserver will block until the callbacks

+  // are finished. Observers should implement quick callback functions; if

+  // lengthy operations are needed, the observer should take care to invoke

+  // the operation on an appropriate thread.

   class PowerObserver {

   public:

     // Notification of a change in power status of the computer, such

@@ -53,32 +60,15 @@ class SystemMonitor {
     virtual void OnResume(SystemMonitor*) = 0;

   };

 

-  void AddObserver(PowerObserver* obs) {

-    observer_list_.AddObserver(obs);

-  }

-

-  void RemoveObserver(PowerObserver* obs) {

-    observer_list_.RemoveObserver(obs);

-  }

-

-  void NotifyPowerStateChange() {

-    LOG(INFO) << L"PowerStateChange: " 

-             << (BatteryPower() ? L"On" : L"Off") << L" battery";

-    FOR_EACH_OBSERVER(PowerObserver, observer_list_,

-      OnPowerStateChange(this));

-  }

+  // Add a new observer.

+  // Can be called from any thread.

+  // Must not be called from within a notification callback.

+  void AddObserver(PowerObserver* obs);

 

-  void NotifySuspend() {

-    FOR_EACH_OBSERVER(PowerObserver, observer_list_, OnSuspend(this));

-  }

-

-  void NotifyResume() {

-    FOR_EACH_OBSERVER(PowerObserver, observer_list_, OnResume(this));

-  }

-

-  // Constructor.  

-  // Don't use this; access SystemMonitor via the Singleton.

-  SystemMonitor();

+  // Remove an existing observer.

+  // Can be called from any thread.

+  // Must not be called from within a notification callback.

+  void RemoveObserver(PowerObserver* obs);

 

 #if defined(OS_WIN)

   // Windows-specific handling of a WM_POWERBROADCAST message.

@@ -88,19 +78,33 @@ class SystemMonitor {
 #endif

 

   // Cross-platform handling of a power event.

-  // This is only exposed for testing.

   void ProcessPowerMessage(PowerEvent event_id);

 

+  // Constructor.  

+  // Don't use this; access SystemMonitor via the Singleton.

+  SystemMonitor();

+

  private:

   // Platform-specific method to check whether the system is currently

   // running on battery power.  Returns true if running on batteries,

   // false otherwise.

   bool IsBatteryPower();

 

-  ObserverList<PowerObserver> observer_list_;

+  // Checks the battery status and notifies observers if the battery

+  // status has changed.

+  void BatteryCheck();

+

+  // Functions to trigger notifications.

+  void NotifyPowerStateChange();

+  void NotifySuspend();

+  void NotifyResume();

+

+  scoped_refptr<ObserverListThreadSafe<PowerObserver> > observer_list_;

   bool battery_in_use_;

   bool suspended_;

 

+  base::OneShotTimer<SystemMonitor> delayed_battery_check_;

+

   DISALLOW_COPY_AND_ASSIGN(SystemMonitor);

 };