Fix webrtc HW encode deadlock scenarios.

content/renderer/media/renderer_gpu_video_accelerator_factories.h

 // Copyright 2013 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.
 
 #ifndef CONTENT_RENDERER_MEDIA_RENDERER_GPU_VIDEO_ACCELERATOR_FACTORIES_H_
 #define CONTENT_RENDERER_MEDIA_RENDERER_GPU_VIDEO_ACCELERATOR_FACTORIES_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/threading/thread.h"
 #include "content/common/content_export.h"
 #include "media/filters/gpu_video_accelerator_factories.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/size.h"
 
 namespace base {
 class MessageLoopProxy;
 class WaitableEvent;
 }
 
@@ skipping 110 matching lines @@
   // function.
   scoped_ptr<base::SharedMemory> shared_memory_segment_;
 
   // Bitmap returned by ReadPixels().
   SkBitmap read_pixels_bitmap_;
 
   // Textures returned by the CreateTexture() function.
   std::vector<uint32> created_textures_;
   std::vector<gpu::Mailbox> created_texture_mailboxes_;
 
+  // Renderer thread designated solely to allocate shared memory on. We hide on
+  // it from webrtc to avoid all kinds of deadlocks of varying complexity, which
+  // we would randomly end up in if we wanted to allocate shared memory on the
+  // renderer's ChildThread, as webrtc likes to sleep on it while calling into
+  // encoder via a varying number of indirections and/or while holding critical
+  // sections.
+  // The thread is owned by the original factories, while the proxy is shared
+  // by all clones.
+  scoped_ptr<base::Thread> shm_alloc_thread_;

[Ami GONE FROM CHROMIUM, 2013/09/04 20:47:56]

Previously you said that "the original factories only, which are in the
RenderThreadImpl" but AFAICT RTI::GetGpuFactories doesn't retain a ref to the
Factories it returns, so I don't understand what keeps the original Factories
alive (and thus the shm_alloc_thread_) for the lifetime of Clone()'d Factories.

+  scoped_refptr<base::MessageLoopProxy> shm_alloc_message_loop_;
+
   DISALLOW_COPY_AND_ASSIGN(RendererGpuVideoAcceleratorFactories);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_RENDERER_GPU_VIDEO_ACCELERATOR_FACTORIES_H_