cc: Fail more visibly when sync queries are not working correctly.

Instead of creating an infinite number of sync queries, which will
eventually cause performance issues, log an error message and block
until oldest query has passed when reaching 16 pending queries.

BUG=371530

Review URL: https://codereview.chromium.org/280543003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270265 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 18 insertions, 0 deletions

diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index 8e60f94..df3ddfd 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -175,6 +175,10 @@ SamplerType SamplerTypeFromTextureTarget(GLenum target) {
 // determine when anti-aliasing is unnecessary.
 const float kAntiAliasingEpsilon = 1.0f / 1024.0f;
 
+// Block or crash if the number of pending sync queries reach this high as
+// something is seriously wrong on the service side if this happens.
+const size_t kMaxPendingSyncQueries = 16;
+
 }  // anonymous namespace
 
 class GLRenderer::ScopedUseGrContext {
@@ -248,6 +252,11 @@ class GLRenderer::SyncQuery {
     return !available;
   }
 
+  void Wait() {
+    unsigned result = 0;
+    gl_->GetQueryObjectuivEXT(query_id_, GL_QUERY_RESULT_EXT, &result);
+  }
+
  private:
   class Fence : public ResourceProvider::Fence {
    public:
@@ -441,6 +450,15 @@ void GLRenderer::BeginDrawingFrame(DrawingFrame* frame) {
 
   scoped_refptr<ResourceProvider::Fence> read_lock_fence;
   if (use_sync_query_) {
+    // Block until oldest sync query has passed if the number of pending queries
+    // ever reach kMaxPendingSyncQueries.
+    if (pending_sync_queries_.size() >= kMaxPendingSyncQueries) {
+      LOG(ERROR) << "Reached limit of pending sync queries.";
+
+      pending_sync_queries_.front()->Wait();
+      DCHECK(!pending_sync_queries_.front()->IsPending());
+    }
+
     while (!pending_sync_queries_.empty()) {
       if (pending_sync_queries_.front()->IsPending())
         break;