Re-land: gpu: Add CHROMIUM_sync_query extension.

gpu/command_buffer/service/query_manager.cc

Index: gpu/command_buffer/service/query_manager.cc
diff --git a/gpu/command_buffer/service/query_manager.cc b/gpu/command_buffer/service/query_manager.cc
index 9f1d3a7169c31b5c1ee640b07f6c08a71623b18b..b288c85263f4c5855017d4670b0c756aff8bdf8d 100644
--- a/gpu/command_buffer/service/query_manager.cc
+++ b/gpu/command_buffer/service/query_manager.cc
@@ -389,6 +389,76 @@ void GetErrorQuery::Destroy(bool /* have_context */) {
 GetErrorQuery::~GetErrorQuery() {
 }
 
+class CommandsCompletedQuery : public QueryManager::Query {
+ public:
+  CommandsCompletedQuery(QueryManager* manager,
+                         GLenum target,
+                         int32 shm_id,
+                         uint32 shm_offset,
+                         bool use_arb_sync);
+
+  // Overridden from QueryManager::Query:
+  virtual bool Begin() OVERRIDE;
+  virtual bool End(base::subtle::Atomic32 submit_count) OVERRIDE;
+  virtual bool Process() OVERRIDE;
+  virtual void Destroy(bool have_context) OVERRIDE;
+
+ protected:
+  virtual ~CommandsCompletedQuery();
+
+ private:
+  bool use_arb_sync_;
+  GLsync sync_;
+};
+
+CommandsCompletedQuery::CommandsCompletedQuery(QueryManager* manager,
+                                               GLenum target,
+                                               int32 shm_id,
+                                               uint32 shm_offset,
+                                               bool use_arb_sync)
+    : Query(manager, target, shm_id, shm_offset),
+      use_arb_sync_(use_arb_sync),
+      sync_(NULL) {}
+
+bool CommandsCompletedQuery::Begin() {
+  if (sync_) {
+    glDeleteSync(sync_);
+    sync_ = NULL;
+  }
+  return true;
+}
+
+bool CommandsCompletedQuery::End(base::subtle::Atomic32 submit_count) {
+  if (use_arb_sync_) {
+    sync_ = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);

[no sievers, 2014/04/15 18:41:15]

You have to glFlush() somewhere or the commands might never complete.

Can you just use the GLFence class here?

[no sievers, 2014/04/15 18:48:44]

"Querying the GL_QUERY_RESULT implicitly flushes the GL pipeline". So we could
also defer it, if that's not already happening somewhere on the service-side.
That would make it more efficient for clients that insert a lot of these queries
per frame.

[reveman, 2014/04/15 22:29:28]

As I mentioned above, the idea is to make the client responsible for this. I
think it would be a bit weird if the client didn't have to call glFlush.
Ah, wasn't aware of this class. Done.

+    DCHECK(sync_);
+  } else {
+    TRACE_EVENT0("gpu", "CommandsCompletedQuery::End");
+    glFinish();  // Poor man's GPU fence.

[no sievers, 2014/04/15 18:41:15]

Do we need this fallback, or can we not support the query?
I think GLFence should give us pretty good coverage across platforms (esp. if we
add es3).

[reveman, 2014/04/15 22:29:28]

We'll need a fall-back somewhere but maybe it should just be software
compositing. Changed latest patch so it's up to the client to handle this
instead.

+  }
+  return AddToPendingQueue(submit_count);
+}
+
+bool CommandsCompletedQuery::Process() {
+  if (sync_) {
+    int value = GL_UNSIGNALED;
+    glGetSynciv(sync_, GL_SYNC_STATUS, 1, NULL, &value);

[no sievers, 2014/04/15 18:41:15]

See comment in gl_fence.cc that this does not work on OSX 10.7. It uses
glClientWaitSync() != GL_TIMEOUT_EXPIRED instead.

[reveman, 2014/04/15 22:29:28]

Ok, makes sense to use GLFence and handle these type of workarounds in one
place.

+    if (value == GL_UNSIGNALED)
+      return true;
+  }
+  return MarkAsCompleted(0);
+}
+
+void CommandsCompletedQuery::Destroy(bool have_context) {
+  if (have_context && !IsDeleted()) {
+    if (sync_)
+      glDeleteSync(sync_);
+    MarkAsDeleted();
+  }
+}
+
+CommandsCompletedQuery::~CommandsCompletedQuery() {}
+
 QueryManager::QueryManager(
     GLES2Decoder* decoder,
     FeatureInfo* feature_info)
@@ -399,6 +469,7 @@ QueryManager::QueryManager(
       use_arb_occlusion_query_for_occlusion_query_boolean_(
           feature_info->feature_flags(
             ).use_arb_occlusion_query_for_occlusion_query_boolean),
+      use_arb_sync_(feature_info->feature_flags().arb_sync),
       query_count_(0) {
   DCHECK(!(use_arb_occlusion_query_for_occlusion_query_boolean_ &&
            use_arb_occlusion_query2_for_occlusion_query_boolean_));
@@ -444,6 +515,10 @@ QueryManager::Query* QueryManager::CreateQuery(
     case GL_GET_ERROR_QUERY_CHROMIUM:
       query = new GetErrorQuery(this, target, shm_id, shm_offset);
       break;
+    case GL_COMMANDS_COMPLETED_CHROMIUM:
+      query = new CommandsCompletedQuery(
+          this, target, shm_id, shm_offset, use_arb_sync_);
+      break;
     default: {
       GLuint service_id = 0;
       glGenQueriesARB(1, &service_id);