cc: Enforce correct recycling in resource pool.

cc/resource_pool.cc

 // Copyright 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 "cc/resource_pool.h"
 
 #include "cc/resource_provider.h"
 
 namespace cc {
 
@@ skipping 25 matching lines @@
 ResourcePool::~ResourcePool() {
   SetMaxMemoryUsageBytes(0);
 }
 
 scoped_ptr<ResourcePool::Resource> ResourcePool::AcquireResource(
     const gfx::Size& size, GLenum format) {
   for (ResourceList::iterator it = resources_.begin();
        it != resources_.end(); ++it) {
     Resource* resource = *it;
 
+    // TODO(epenner): It would be nice to DCHECK that this
+    // doesn't happen two frames in a row for any resource
+    // in this pool.
+    if (!resource_provider_->canLockForWrite(resource->id()))
+      continue;
+
     if (resource->size() != size)
       continue;
     if (resource->format() != format)
       continue;
 
     resources_.erase(it);
     return make_scoped_ptr(resource);
   }
 
   // Create new resource.
   Resource* resource = new Resource(
       resource_provider_, size, format);
+
+  // Extend all read locks on all resources until the resource is
+  // finished being used, such that we know when resources are
+  // truly safe to recycle.
+  resource_provider_->enableReadLockFences(resource->id(), true);
+
   memory_usage_bytes_ += resource->bytes();
   return make_scoped_ptr(resource);
 }
 
 void ResourcePool::ReleaseResource(
     scoped_ptr<ResourcePool::Resource> resource) {
   if (memory_usage_bytes_ > max_memory_usage_bytes_) {
     memory_usage_bytes_ -= resource->bytes();
     return;
   }
 
   resources_.push_back(resource.release());
 }
 
 void ResourcePool::SetMaxMemoryUsageBytes(size_t max_memory_usage_bytes) {
   max_memory_usage_bytes_ = max_memory_usage_bytes;
 
   while (!resources_.empty()) {
     if (memory_usage_bytes_ <= max_memory_usage_bytes_)
       break;
     Resource* resource = resources_.front();
     resources_.pop_front();
     memory_usage_bytes_ -= resource->bytes();
     delete resource;
   }
 }
 
 }  // namespace cc