gpu: Allow fences to check whether a flush has occurred

ui/gl/gl_fence.cc

 // 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.
 
 #include "ui/gl/gl_fence.h"
 
 #include "base/compiler_specific.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_context.h"
 
 namespace {
 
 class GLFenceNVFence: public gfx::GLFence {
  public:
   GLFenceNVFence(bool flush) {
     // What if either of these GL calls fails? TestFenceNV will return true.
     // See spec:
     // http://www.opengl.org/registry/specs/NV/fence.txt
     //
     // What should happen if TestFenceNV is called for a name before SetFenceNV
     // is called?
     //     We generate an INVALID_OPERATION error, and return TRUE.
     //     This follows the semantics for texture object names before
     //     they are bound, in that they acquire their state upon binding.
     //     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 {
     return !!glTestFenceNV(fence_);
   }
 
   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:
   virtual ~GLFenceNVFence() {
     glDeleteFencesNV(1, &fence_);
   }
 
   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 {
     // Handle the case where FenceSync failed.
     if (!sync_)
       return true;
 
     // We could potentially use glGetSynciv here, but it doesn't work
     // on OSX 10.7 (always says the fence is not signaled yet).
     // glClientWaitSync works better, so let's use that instead.
     return  glClientWaitSync(sync_, 0, 0) != GL_TIMEOUT_EXPIRED;
   }
 
   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:
   virtual ~GLFenceARBSync() {
     glDeleteSync(sync_);
   }
 
   GLsync sync_;
+  scoped_refptr<gfx::GLContext::FlushEvent> flush_event_;
 };
 
 #if !defined(OS_MACOSX)
 class EGLFenceSync : public gfx::GLFence {
  public:
   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 {
     EGLint value = 0;
     eglGetSyncAttribKHR(display_, sync_, EGL_SYNC_STATUS_KHR, &value);
     DCHECK(value == EGL_SIGNALED_KHR || value == EGL_UNSIGNALED_KHR);
     return !value || value == EGL_SIGNALED_KHR;
   }
 
   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();
+    }
   }
 
 
  private:
   virtual ~EGLFenceSync() {
     eglDestroySyncKHR(display_, sync_);
   }
 
   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);
 #endif
   if (gfx::g_driver_gl.ext.b_GL_NV_fence)
     return new GLFenceNVFence(flush);
   if (gfx::g_driver_gl.ext.b_GL_ARB_sync)
     return new GLFenceARBSync(flush);
   return NULL;
 }
@@ skipping 10 matching lines @@
 
 GLFence* GLFence::Create() {
   return CreateFence(true);
 }
 
 GLFence* GLFence::CreateWithoutFlush() {
   return CreateFence(false);
 }
 
 }  // namespace gfx