exo: Handle lost context situations properly.

components/exo/buffer.cc

Index: components/exo/buffer.cc
diff --git a/components/exo/buffer.cc b/components/exo/buffer.cc
index 2f229ad65aa03a11715facc269442a50791ae877..0895558bec4c97ea65c677b4b7137374bdb5863e 100644
--- a/components/exo/buffer.cc
+++ b/components/exo/buffer.cc
@@ -49,32 +49,58 @@ GLenum GLInternalFormat(gfx::BufferFormat format) {
   return kGLInternalFormats[static_cast<int>(format)];
 }
 
-gpu::gles2::GLES2Interface* GetContextGL() {
-  ui::ContextFactory* context_factory =
-      aura::Env::GetInstance()->context_factory();
-  return context_factory->SharedMainThreadContextProvider()->ContextGL();
-}
-
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
-// Buffer, public:
+// Buffer::Texture
 
-Buffer::Buffer(scoped_ptr<gfx::GpuMemoryBuffer> gpu_memory_buffer,
-               unsigned texture_target)
-    : gpu_memory_buffer_(gpu_memory_buffer.Pass()),
+// Encapsulates the state and logic needed to bind a buffer to a GLES2 texture.
+class Buffer::Texture {
+ public:
+  Texture(gfx::GpuMemoryBuffer* gpu_memory_buffer,
+          cc::ContextProvider* context_provider,
+          unsigned texture_target);
+  ~Texture();
+
+  // Returns true if GLES2 resources for texture have been lost.
+  bool IsLost();
+
+  // Binds the content of gpu memory buffer to the texture returned by
+  // mailbox(). Returns a sync token that can be used to when accessing texture
+  // from a different context.
+  gpu::SyncToken BindTexImage();
+
+  // Releases the content of gpu memory buffer after |sync_token| has passed.
+  void ReleaseTexImage(const gpu::SyncToken& sync_token);
+
+  // Returns the mailbox for this texture.
+  gpu::Mailbox mailbox() const { return mailbox_; }
+
+ private:
+  scoped_refptr<cc::ContextProvider> context_provider_;
+  const unsigned texture_target_;
+  const gfx::Size size_;
+  unsigned image_id_;
+  unsigned texture_id_;
+  gpu::Mailbox mailbox_;
+
+  DISALLOW_COPY_AND_ASSIGN(Texture);
+};
+
+Buffer::Texture::Texture(gfx::GpuMemoryBuffer* gpu_memory_buffer,
+                         cc::ContextProvider* context_provider,
+                         unsigned texture_target)
+    : context_provider_(context_provider),
       texture_target_(texture_target),
-      texture_id_(0),
-      image_id_(0) {
-  gpu::gles2::GLES2Interface* gles2 = GetContextGL();
-  // Create an image for |gpu_memory_buffer_|.
-  gfx::Size size = gpu_memory_buffer_->GetSize();
+      size_(gpu_memory_buffer->GetSize()),
+      image_id_(0),
+      texture_id_(0) {
+  gpu::gles2::GLES2Interface* gles2 = context_provider_->ContextGL();
   image_id_ = gles2->CreateImageCHROMIUM(
-      gpu_memory_buffer_->AsClientBuffer(), size.width(), size.height(),
-      GLInternalFormat(gpu_memory_buffer_->GetFormat()));
-  // Create a texture with |texture_target_|.
-  gles2->ActiveTexture(GL_TEXTURE0);
+      gpu_memory_buffer->AsClientBuffer(), size_.width(), size_.height(),
+      GLInternalFormat(gpu_memory_buffer->GetFormat()));
   gles2->GenTextures(1, &texture_id_);
+  gles2->ActiveTexture(GL_TEXTURE0);
   gles2->BindTexture(texture_target_, texture_id_);
   gles2->TexParameteri(texture_target_, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
   gles2->TexParameteri(texture_target_, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
@@ -85,54 +111,98 @@ Buffer::Buffer(scoped_ptr<gfx::GpuMemoryBuffer> gpu_memory_buffer,
   gles2->ProduceTextureCHROMIUM(texture_target_, mailbox_.name);
 }
 
-Buffer::~Buffer() {
-  gpu::gles2::GLES2Interface* gles2 = GetContextGL();
-  if (texture_id_)
-    gles2->DeleteTextures(1, &texture_id_);
-  if (image_id_)
-    gles2->DestroyImageCHROMIUM(image_id_);
+Buffer::Texture::~Texture() {
+  gpu::gles2::GLES2Interface* gles2 = context_provider_->ContextGL();
+  gles2->ActiveTexture(GL_TEXTURE0);
+  gles2->DeleteTextures(1, &texture_id_);
+  gles2->DestroyImageCHROMIUM(image_id_);
+}
+
+bool Buffer::Texture::IsLost() {
+  gpu::gles2::GLES2Interface* gles2 = context_provider_->ContextGL();
+  return gles2->GetGraphicsResetStatusKHR() != GL_NO_ERROR;
+}
+
+gpu::SyncToken Buffer::Texture::BindTexImage() {
+  gpu::gles2::GLES2Interface* gles2 = context_provider_->ContextGL();
+  gles2->ActiveTexture(GL_TEXTURE0);
+  gles2->BindTexture(texture_target_, texture_id_);
+  gles2->BindTexImage2DCHROMIUM(texture_target_, image_id_);
+  // Create and return a sync token that can be used to ensure that the
+  // BindTexImage2DCHROMIUM call is processed before issuing any commands
+  // that will read from the texture on a different context.
+  uint64 fence_sync = gles2->InsertFenceSyncCHROMIUM();
+  gles2->OrderingBarrierCHROMIUM();
+  gpu::SyncToken sync_token;
+  gles2->GenUnverifiedSyncTokenCHROMIUM(fence_sync, sync_token.GetData());
+  return sync_token;
+}
+
+void Buffer::Texture::ReleaseTexImage(const gpu::SyncToken& sync_token) {
+  gpu::gles2::GLES2Interface* gles2 = context_provider_->ContextGL();
+  if (sync_token.HasData())
+    gles2->WaitSyncTokenCHROMIUM(sync_token.GetConstData());
+  gles2->ActiveTexture(GL_TEXTURE0);
+  gles2->BindTexture(texture_target_, texture_id_);
+  gles2->ReleaseTexImage2DCHROMIUM(texture_target_, image_id_);
 }
 
-scoped_ptr<cc::SingleReleaseCallback> Buffer::AcquireTextureMailbox(
+////////////////////////////////////////////////////////////////////////////////
+// Buffer, public:
+
+Buffer::Buffer(scoped_ptr<gfx::GpuMemoryBuffer> gpu_memory_buffer,
+               unsigned texture_target)
+    : gpu_memory_buffer_(gpu_memory_buffer.Pass()),
+      texture_target_(texture_target),
+      use_count_(0) {}
+
+Buffer::~Buffer() {}
+
+scoped_ptr<cc::SingleReleaseCallback> Buffer::ProduceTextureMailbox(
     cc::TextureMailbox* texture_mailbox) {
-  // Buffer can only be used by one client at a time. If texture id is 0, then a
-  // previous call to AcquireTextureMailbox() is using this buffer and it has
-  // not been released yet.
-  if (!texture_id_) {
-    DLOG(WARNING) << "Client tried to use a buffer that has not been released";
+  DLOG_IF(WARNING, use_count_)
+      << "Producing a texture mailbox for a buffer that has not been released";
+
+  // Increment the use count for this buffer.
+  ++use_count_;
+
+  // Note: This can fail if GPU acceleration has been disabled.
+  scoped_refptr<cc::ContextProvider> context_provider =
+      aura::Env::GetInstance()
+          ->context_factory()
+          ->SharedMainThreadContextProvider();
+  if (!context_provider) {
+    DLOG(WARNING) << "Failed to acquire a context provider";
+    Release();  // Decrements the use count
     return nullptr;
   }
 
-  // Take ownerhsip of image and texture ids.
-  unsigned texture_id = 0;
-  unsigned image_id = 0;
-  std::swap(texture_id, texture_id_);
-  DCHECK_NE(image_id_, 0u);
-  std::swap(image_id, image_id_);
+  // Creating a new texture is relatively expensive so we reuse the last
+  // texture whenever possible.
+  scoped_ptr<Texture> texture = last_texture_.Pass();
 
-  // Bind texture to |texture_target_|.
-  gpu::gles2::GLES2Interface* gles2 = GetContextGL();
-  gles2->ActiveTexture(GL_TEXTURE0);
-  gles2->BindTexture(texture_target_, texture_id);
+  // If texture is lost, destroy it to ensure that we create a new one below.
+  if (texture && texture->IsLost())
+    texture.reset();

[piman, 2015/11/23 21:04:42]

I suggest doing this before getting the context_provider, because of potential
races.
texture->IsLost() may be the first thing that learns about the lost context, and
so SharedMainThreadContextProvider() may have returned an "old" channel instead
of recreating one, and when you try to recreate below, things fail.
OTOH, if you check texture first, if it's lost due to a lost channel, you are
guaranteed that SharedMainThreadContextProvider() will recreate a channel.

[reveman, 2015/11/23 23:25:29]

Makes sense. Done.

 
-  // Bind the image to texture.
-  gles2->BindTexImage2DCHROMIUM(texture_target_, image_id);
+  // Create a new texture if one doesn't already exist. The contents of this
+  // buffer can be bound to the texture using a call to BindTexImage and must
+  // be released using a matching ReleaseTexImage call before it can be reused
+  // or destroyed.
+  if (!texture) {
+    texture = make_scoped_ptr(new Texture(
+        gpu_memory_buffer_.get(), context_provider.get(), texture_target_));
+  }
 
-  // Create a sync token to ensure that the BindTexImage2DCHROMIUM call is
-  // processed before issuing any commands that will read from texture.
-  uint64 fence_sync = gles2->InsertFenceSyncCHROMIUM();
-  gles2->ShallowFlushCHROMIUM();
-  gpu::SyncToken sync_token;
-  gles2->GenUnverifiedSyncTokenCHROMIUM(fence_sync, sync_token.GetData());
+  // This binds the latest contents of this buffer to the texture.
+  gpu::SyncToken sync_token = texture->BindTexImage();
 
   bool is_overlay_candidate = false;
   *texture_mailbox =
-      cc::TextureMailbox(mailbox_, sync_token, texture_target_,
+      cc::TextureMailbox(texture->mailbox(), sync_token, texture_target_,
                          gpu_memory_buffer_->GetSize(), is_overlay_candidate);
   return cc::SingleReleaseCallback::Create(
-             base::Bind(&Buffer::Release, AsWeakPtr(), texture_target_,
-                        texture_id, image_id))
-      .Pass();
+      base::Bind(&Buffer::ReleaseTexture, AsWeakPtr(), base::Passed(&texture)));
 }
 
 gfx::Size Buffer::GetSize() const {
@@ -142,8 +212,9 @@ gfx::Size Buffer::GetSize() const {
 scoped_refptr<base::trace_event::TracedValue> Buffer::AsTracedValue() const {
   scoped_refptr<base::trace_event::TracedValue> value =
       new base::trace_event::TracedValue;
-  value->SetInteger("width", GetSize().width());
-  value->SetInteger("height", GetSize().height());
+  gfx::Size size = gpu_memory_buffer_->GetSize();
+  value->SetInteger("width", size.width());
+  value->SetInteger("height", size.height());
   value->SetInteger("format",
                     static_cast<int>(gpu_memory_buffer_->GetFormat()));
   return value;
@@ -152,36 +223,36 @@ scoped_refptr<base::trace_event::TracedValue> Buffer::AsTracedValue() const {
 ////////////////////////////////////////////////////////////////////////////////
 // Buffer, private:
 
+void Buffer::Release() {
+  DCHECK_GT(use_count_, 0u);
+  if (--use_count_)
+    return;
+
+  // Run release callback to notify the client that buffer has been released.
+  if (!release_callback_.is_null())
+    release_callback_.Run();
+}
+
 // static
-void Buffer::Release(base::WeakPtr<Buffer> buffer,
-                     unsigned texture_target,
-                     unsigned texture_id,
-                     unsigned image_id,
-                     const gpu::SyncToken& sync_token,
-                     bool is_lost) {
-  TRACE_EVENT1("exo", "Buffer::Release", "is_lost", is_lost);
-
-  gpu::gles2::GLES2Interface* gles2 = GetContextGL();
-  if (sync_token.HasData())
-    gles2->WaitSyncTokenCHROMIUM(sync_token.GetConstData());
-  gles2->ActiveTexture(GL_TEXTURE0);
-  gles2->BindTexture(texture_target, texture_id);
-  gles2->ReleaseTexImage2DCHROMIUM(texture_target, image_id);
+void Buffer::ReleaseTexture(base::WeakPtr<Buffer> buffer,
+                            scoped_ptr<Texture> texture,
+                            const gpu::SyncToken& sync_token,
+                            bool is_lost) {
+  TRACE_EVENT1("exo", "Buffer::ReleaseTexture", "is_lost", is_lost);
+
+  // Release image so it can safely be reused or destroyed.
+  texture->ReleaseTexImage(sync_token);
 
-  // Delete resources and return if buffer is gone.
-  if (!buffer) {
-    gles2->DeleteTextures(1, &texture_id);
-    gles2->DestroyImageCHROMIUM(image_id);
+  // Early out if buffer is gone. This can happen when the client destroyed the
+  // buffer before receiving a release callback.
+  if (!buffer)
     return;
-  }
 
-  DCHECK_EQ(buffer->texture_id_, 0u);
-  buffer->texture_id_ = texture_id;
-  DCHECK_EQ(buffer->image_id_, 0u);
-  buffer->image_id_ = image_id;
+  // Allow buffer to reused texture if it's not lost.
+  if (!is_lost)
+    buffer->last_texture_ = texture.Pass();
 
-  if (!buffer->release_callback_.is_null())
-    buffer->release_callback_.Run();
+  buffer->Release();
 }
 
 }  // namespace exo