aw: Track UI request GL separately from other threads

android_webview/browser/deferred_gpu_command_service.cc

Index: android_webview/browser/deferred_gpu_command_service.cc
diff --git a/android_webview/browser/deferred_gpu_command_service.cc b/android_webview/browser/deferred_gpu_command_service.cc
index 8a137a8e7883f0ee76c8b59fa1e01e51fdf0a211..cb13cd77b1c7809ff75b3b94be740ea55ad477ac 100644
--- a/android_webview/browser/deferred_gpu_command_service.cc
+++ b/android_webview/browser/deferred_gpu_command_service.cc
@@ -20,6 +20,7 @@ class ThreadSafeBool {
   ThreadSafeBool();
   void Set(bool boolean);
   bool Get();
+  bool GetAndSet();
 
  private:
   base::Lock lock_;
@@ -35,6 +36,13 @@ void ThreadSafeBool::Set(bool boolean) {
   boolean_ = boolean;
 }
 
+bool ThreadSafeBool::GetAndSet() {
+  base::AutoLock lock(lock_);
+  bool rv = boolean_;
+  boolean_ = true;
+  return rv;
+}
+
 bool ThreadSafeBool::Get() {
   base::AutoLock lock(lock_);
   return boolean_;
@@ -43,6 +51,11 @@ bool ThreadSafeBool::Get() {
 base::LazyInstance<ThreadSafeBool> g_request_pending =
     LAZY_INSTANCE_INITIALIZER;
 
+// Because request is posted to UI thread, have to treat requests on UI thread
+// specifically because UI can immediately block waiting for the request.
+base::LazyInstance<ThreadSafeBool> g_request_pending_on_ui =
+    LAZY_INSTANCE_INITIALIZER;
+
 base::LazyInstance<scoped_refptr<DeferredGpuCommandService> >
     g_service = LAZY_INSTANCE_INITIALIZER;
 }  // namespace
@@ -65,6 +78,7 @@ ScopedAllowGL::ScopedAllowGL() {
 ScopedAllowGL::~ScopedAllowGL() {
   allow_gl.Get().Set(false);
   g_request_pending.Get().Set(false);
+  g_request_pending_on_ui.Get().Set(false);
 
   DeferredGpuCommandService* service = g_service.Get();
   if (service) {
@@ -83,6 +97,7 @@ void DeferredGpuCommandService::SetInstance() {
 
     // Initialize global booleans.
     g_request_pending.Get().Set(false);
+    g_request_pending_on_ui.Get().Set(false);
   }
 }
 
@@ -109,8 +124,13 @@ void DeferredGpuCommandService::RequestProcessGL() {
     return;
   }
 
-  if (!g_request_pending.Get().Get()) {
-    g_request_pending.Get().Set(true);
+  bool on_ui_thread = renderer_state->CurrentlyOnUIThread();

[hush (inactive), 2014/08/05 23:04:39]

on_ui_thread only means render state was running on UI thread during that point
of time. But it does not mean renderer state won't switch threads, nor does it
mean UI is blocked on a request to RT.

DeferredGpuCommandService::RequestProcessGL can be running on any thread (blink
main thread, UI thread, and render thread)
Suppose DeferredGpuCommandService::RequestProcessGL is running on blink main
thread now, and right after this line, render state hops from UI thread to
Render Thread. 

Will this be a problem?

[boliu, 2014/08/05 23:07:55]

That's how things work today, before or after this CL. What problem are you
talking about?

+  bool need_request = on_ui_thread ? !g_request_pending_on_ui.Get().GetAndSet()
+                                   : !g_request_pending.Get().GetAndSet();
+  if (need_request) {
+    if (on_ui_thread) {
+      g_request_pending.Get().Set(true);
+    }

[hush (inactive), 2014/08/05 23:04:39]

if g_request_pending_on_ui is true, g_request_pending is definitely true.
Right?
If so, we can just set g_request_pending regardless, and treat
g_request_pending_on_ui separately

[boliu, 2014/08/05 23:07:55]

Yep, that's what I wanted to do here.
You mean remove if (on_ui_thread)? Yeah that should work.

[hush (inactive), 2014/08/05 23:55:15]

yes. if on_ui_thread is false, you will set g_request_pending in line 129. If it
is true, you will do that line 132.
On 2014/08/05 23:07:55, boliu wrote:

[boliu, 2014/08/06 00:05:46]

Done.

     renderer_state->ClientRequestDrawGL();
   }
 }