gpu: Allow fences to check whether a flush has occurred

ui/gl/gl_fence.cc

Index: ui/gl/gl_fence.cc
diff --git a/ui/gl/gl_fence.cc b/ui/gl/gl_fence.cc
index 1790f864415f12788297152e9c9645557b834cc5..97f48bab5b383957c9fdd8e6f289ee977c2c8142 100644
--- a/ui/gl/gl_fence.cc
+++ b/ui/gl/gl_fence.cc
@@ -25,8 +25,11 @@ class GLFenceNVFence: public gfx::GLFence {
     //     We will arbitrarily return TRUE for consistency.
     glGenFencesNV(1, &fence_);
     glSetFenceNV(fence_, GL_ALL_COMPLETED_NV);
-    if (flush)
+    if (flush) {
       glFlush();
+    } else {
+      flush_event_ = gfx::GLContext::GetCurrent()->SignalFlush();
+    }
   }
 
   virtual bool HasCompleted() OVERRIDE {
@@ -34,11 +37,16 @@ class GLFenceNVFence: public gfx::GLFence {
   }
 
   virtual void ClientWait() OVERRIDE {
-    glFinishFenceNV(fence_);
+    if (flush_event_->IsSignaled()) {

[piman, 2014/03/15 00:18:40]

(here an below), you also need to check for flush_event_ being NULL (for the
create-with-flush case).

[no sievers, 2014/03/19 01:25:21]

Done.

+      glFinishFenceNV(fence_);
+    } else {
+      LOG(ERROR) << "Trying to wait for uncommitted fence. Skipping...";
+      NOTREACHED();

[piman, 2014/03/15 00:18:40]

Maybe remove the NOTREACHED. It can be reached from untrusted clients.

[no sievers, 2014/03/19 01:25:21]

Done.

+    }
   }
 
   virtual void ServerWait() OVERRIDE {
-    glFinishFenceNV(fence_);
+    ClientWait();
   }
 
  private:
@@ -47,14 +55,18 @@ class GLFenceNVFence: public gfx::GLFence {
   }
 
   GLuint fence_;
+  scoped_refptr<gfx::GLContext::FlushEvent> flush_event_;
 };
 
 class GLFenceARBSync: public gfx::GLFence {
  public:
   GLFenceARBSync(bool flush) {
     sync_ = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
-    if (flush)
+    if (flush) {
       glFlush();
+    } else {
+      flush_event_ = gfx::GLContext::GetCurrent()->SignalFlush();
+    }
   }
 
   virtual bool HasCompleted() OVERRIDE {
@@ -69,11 +81,21 @@ class GLFenceARBSync: public gfx::GLFence {
   }
 
   virtual void ClientWait() OVERRIDE {
-    glClientWaitSync(sync_, GL_SYNC_FLUSH_COMMANDS_BIT, GL_TIMEOUT_IGNORED);
+    if (flush_event_->IsSignaled()) {
+      glClientWaitSync(sync_, GL_SYNC_FLUSH_COMMANDS_BIT, GL_TIMEOUT_IGNORED);
+    } else {
+      LOG(ERROR) << "Trying to wait for uncommitted fence. Skipping...";
+      NOTREACHED();
+    }
   }
 
   virtual void ServerWait() OVERRIDE {
-    glWaitSync(sync_, 0, GL_TIMEOUT_IGNORED);
+    if (flush_event_->IsSignaled()) {
+      glWaitSync(sync_, 0, GL_TIMEOUT_IGNORED);
+    } else {
+      LOG(ERROR) << "Trying to wait for uncommitted fence. Skipping...";
+      NOTREACHED();
+    }
   }
 
  private:
@@ -82,6 +104,7 @@ class GLFenceARBSync: public gfx::GLFence {
   }
 
   GLsync sync_;
+  scoped_refptr<gfx::GLContext::FlushEvent> flush_event_;
 };
 
 #if !defined(OS_MACOSX)
@@ -90,8 +113,11 @@ class EGLFenceSync : public gfx::GLFence {
   EGLFenceSync(bool flush) {
     display_ = eglGetCurrentDisplay();
     sync_ = eglCreateSyncKHR(display_, EGL_SYNC_FENCE_KHR, NULL);
-    if (flush)
+    if (flush) {
       glFlush();
+    } else {
+      flush_event_ = gfx::GLContext::GetCurrent()->SignalFlush();
+    }
   }
 
   virtual bool HasCompleted() OVERRIDE {
@@ -102,14 +128,24 @@ class EGLFenceSync : public gfx::GLFence {
   }
 
   virtual void ClientWait() OVERRIDE {
-    EGLint flags = 0;
-    EGLTimeKHR time = EGL_FOREVER_KHR;
-    eglClientWaitSyncKHR(display_, sync_, flags, time);
+    if (flush_event_->IsSignaled()) {
+      EGLint flags = 0;
+      EGLTimeKHR time = EGL_FOREVER_KHR;
+      eglClientWaitSyncKHR(display_, sync_, flags, time);
+    } else {
+      LOG(ERROR) << "Trying to wait for uncommitted fence. Skipping...";
+      NOTREACHED();
+    }
   }
 
   virtual void ServerWait() OVERRIDE {
-    EGLint flags = 0;
-    eglWaitSyncKHR(display_, sync_, flags);
+    if (flush_event_->IsSignaled()) {
+      EGLint flags = 0;
+      eglWaitSyncKHR(display_, sync_, flags);
+    } else {
+      LOG(ERROR) << "Trying to wait for uncommitted fence. Skipping...";
+      NOTREACHED();
+    }
   }
 
 
@@ -120,11 +156,16 @@ class EGLFenceSync : public gfx::GLFence {
 
   EGLSyncKHR sync_;
   EGLDisplay display_;
+  scoped_refptr<gfx::GLContext::FlushEvent> flush_event_;
 };
 #endif // !OS_MACOSX
 
 // static
 gfx::GLFence* CreateFence(bool flush) {
+  if (!gfx::GLContext::GetCurrent()) {

[piman, 2014/03/15 00:18:40]

nit: simply DCHECK(gfx::GLContext::GetCurrent()) ?

[no sievers, 2014/03/19 01:25:21]

Done.

+    NOTREACHED() << "Trying to create fence with no context";
+    return NULL;
+  }  
 #if !defined(OS_MACOSX)
   if (gfx::g_driver_egl.ext.b_EGL_KHR_fence_sync)
     return new EGLFenceSync(flush);