Replace ScopedThreadProxy with MessageLoopProxy & WeakPtrs.

This affects the following classes:
* ChromotingClient
* ChromotingInstance
* HostUserInterface
* It2MeHostUserInterface

The MessageLoopProxy/WeakPtr combination requires that the WeakPtr is created on the thread referred to by the proxy; code in which that is hard to arrange usually has subtle race-conditions.

TEST=Existing unit-tests, and manual testing.


Review URL: https://chromiumcodereview.appspot.com/10454040

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@139623 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 30 insertions, 30 deletions

diff --git a/remoting/client/plugin/chromoting_instance.cc b/remoting/client/plugin/chromoting_instance.cc
index fec261e..28556b4 100644
--- a/remoting/client/plugin/chromoting_instance.cc
+++ b/remoting/client/plugin/chromoting_instance.cc
@@ -97,7 +97,10 @@ std::string ConnectionErrorToString(ChromotingInstance::ConnectionError error) {
 // while sending the log message to the UI.
 static bool g_logging_to_plugin = false;
 static bool g_has_logging_instance = false;
-static ChromotingInstance* g_logging_instance = NULL;
+CR_DEFINE_STATIC_LOCAL(
+    scoped_refptr<base::SingleThreadTaskRunner>, g_logging_task_runner, ());
+CR_DEFINE_STATIC_LOCAL(
+    base::WeakPtr<ChromotingInstance>, g_logging_instance, ());
 static logging::LogMessageHandlerFunction g_logging_old_handler = NULL;
 
 static base::LazyInstance<base::Lock>::Leaky
@@ -139,7 +142,7 @@ ChromotingInstance::ChromotingInstance(PP_Instance pp_instance)
       plugin_message_loop_(
           new PluginMessageLoopProxy(&plugin_thread_delegate_)),
       context_(plugin_message_loop_),
-      thread_proxy_(new ScopedThreadProxy(plugin_message_loop_)) {
+      weak_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
   RequestInputEvents(PP_INPUTEVENT_CLASS_MOUSE | PP_INPUTEVENT_CLASS_WHEEL);
   RequestFilteringInputEvents(PP_INPUTEVENT_CLASS_KEYBOARD);
 
@@ -157,10 +160,6 @@ ChromotingInstance::ChromotingInstance(PP_Instance pp_instance)
 ChromotingInstance::~ChromotingInstance() {
   DCHECK(plugin_message_loop_->BelongsToCurrentThread());
 
-  // Detach the log proxy so we don't log anything else to the UI.
-  // This needs to be done before the instance is unregistered for logging.
-  thread_proxy_->Detach();
-
   // Unregister this instance so that debug log messages will no longer be sent
   // to it. This will stop all logging in all Chromoting instances.
   UnregisterLoggingInstance();
@@ -175,10 +174,7 @@ ChromotingInstance::~ChromotingInstance() {
   // Stopping the context shuts down all chromoting threads.
   context_.Stop();
 
-  // Delete |thread_proxy_| before we detach |plugin_message_loop_|,
-  // otherwise ScopedThreadProxy may DCHECK when being destroyed.
-  thread_proxy_.reset();
-
+  // Ensure that nothing touches the plugin thread delegate after this point.
   plugin_message_loop_->Detach();
 }
 
@@ -614,7 +610,8 @@ void ChromotingInstance::RegisterLoggingInstance() {
   // and display them to the user.
   // If multiple plugins are run, then the last one registered will handle all
   // logging for all instances.
-  g_logging_instance = this;
+  g_logging_instance = weak_factory_.GetWeakPtr();
+  g_logging_task_runner = plugin_message_loop_;
   g_has_logging_instance = true;
 }
 
@@ -622,12 +619,13 @@ void ChromotingInstance::UnregisterLoggingInstance() {
   base::AutoLock lock(g_logging_lock.Get());
 
   // Don't unregister unless we're the currently registered instance.
-  if (this != g_logging_instance)
+  if (this != g_logging_instance.get())
     return;
 
   // Unregister this instance for logging.
   g_has_logging_instance = false;
-  g_logging_instance = NULL;
+  g_logging_instance.reset();
+  g_logging_task_runner = NULL;
 
   VLOG(1) << "Unregistering global log handler";
 }
@@ -649,24 +647,26 @@ bool ChromotingInstance::LogToUI(int severity, const char* file, int line,
   // the lock and check |g_logging_instance| unnecessarily. This is not
   // problematic because we always set |g_logging_instance| inside a lock.
   if (g_has_logging_instance) {
-    // Do not LOG anything while holding this lock or else the code will
-    // deadlock while trying to re-get the lock we're already in.
-    base::AutoLock lock(g_logging_lock.Get());
-    if (g_logging_instance &&
-        // If |g_logging_to_plugin| is set and we're on the logging thread, then
-        // this LOG message came from handling a previous LOG message and we
-        // should skip it to avoid an infinite loop of LOG messages.
-        // We don't have a lock around |g_in_processtoui|, but that's OK since
-        // the value is only read/written on the logging thread.
-        (!g_logging_instance->plugin_message_loop_->BelongsToCurrentThread() ||
-         !g_logging_to_plugin)) {
+    scoped_refptr<base::SingleThreadTaskRunner> logging_task_runner;
+
+    {
+      base::AutoLock lock(g_logging_lock.Get());
+      // If we're on the logging thread and |g_logging_to_plugin| is set then
+      // this LOG message came from handling a previous LOG message and we
+      // should skip it to avoid an infinite loop of LOG messages.
+      if (!g_logging_task_runner->BelongsToCurrentThread() ||
+          !g_logging_to_plugin) {
+        logging_task_runner = g_logging_task_runner;
+      }
+    }
+
+    if (logging_task_runner.get()) {
       std::string message = remoting::GetTimestampString();
       message += (str.c_str() + message_start);
-      // |thread_proxy_| is safe to use here because we detach it before
-      // tearing down the |g_logging_instance|.
-      g_logging_instance->thread_proxy_->PostTask(
+
+      g_logging_task_runner->PostTask(
           FROM_HERE, base::Bind(&ChromotingInstance::ProcessLogToUI,
-                                base::Unretained(g_logging_instance), message));
+                                g_logging_instance, message));
     }
   }
 
@@ -681,6 +681,7 @@ void ChromotingInstance::ProcessLogToUI(const std::string& message) {
   // This flag (which is set only here) is used to prevent LogToUI from posting
   // new tasks while we're in the middle of servicing a LOG call. This can
   // happen if the call to LogDebugInfo tries to LOG anything.
+  // Since it is read on the plugin thread, we don't need to lock to set it.
   g_logging_to_plugin = true;
   ChromotingScriptableObject* scriptable_object = GetScriptableObject();
   if (scriptable_object) {
diff --git a/remoting/client/plugin/chromoting_instance.h b/remoting/client/plugin/chromoting_instance.h
index a489bde..0f1bdde 100644
--- a/remoting/client/plugin/chromoting_instance.h
+++ b/remoting/client/plugin/chromoting_instance.h
@@ -25,7 +25,6 @@
 #endif
 
 #include "ppapi/cpp/private/instance_private.h"
-#include "remoting/base/scoped_thread_proxy.h"
 #include "remoting/client/client_context.h"
 #include "remoting/client/key_event_mapper.h"
 #include "remoting/client/plugin/mac_key_event_processor.h"
@@ -225,7 +224,7 @@ class ChromotingInstance :
   // This wraps a ChromotingScriptableObject in a pp::Var.
   pp::Var instance_object_;
 
-  scoped_ptr<ScopedThreadProxy> thread_proxy_;
+  base::WeakPtrFactory<ChromotingInstance> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromotingInstance);
 };