V4L2VDA: do not allocate input buffers in GPU child thread.

media/gpu/v4l2_video_decode_accelerator.cc

 // Copyright 2014 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 "media/gpu/v4l2_video_decode_accelerator.h"
 
 #include <dlfcn.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <linux/videodev2.h>
@@ skipping 266 matching lines @@
   // Subscribe to the resolution change event.
   struct v4l2_event_subscription sub;
   memset(&sub, 0, sizeof(sub));
   sub.type = V4L2_EVENT_SOURCE_CHANGE;
   IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_SUBSCRIBE_EVENT, &sub);
 
   if (video_profile_ >= H264PROFILE_MIN && video_profile_ <= H264PROFILE_MAX) {
     decoder_h264_parser_.reset(new H264Parser());
   }
 
-  if (!CreateInputBuffers())
-    return false;
-
   decoder_cmd_supported_ = IsDecoderCmdSupported();

[Pawel Osciak, 2016/11/24 08:28:35]

Could this and the subscribe event ioctl above be run on decoder thread as well?

[wuchengli, 2016/11/28 06:13:58]

Done.

 
   if (!decoder_thread_.Start()) {
     LOGF(ERROR) << "decoder thread failed to start";
     return false;
   }
 
-  decoder_state_ = kInitialized;
   output_mode_ = config.output_mode;
 
-  // StartDevicePoll will NOTIFY_ERROR on failure, so IgnoreResult is fine here.
+  // InitializeTask will NOTIFY_ERROR on failure.
   decoder_thread_.task_runner()->PostTask(
-      FROM_HERE, base::Bind(base::IgnoreResult(
-                                &V4L2VideoDecodeAccelerator::StartDevicePoll),
+      FROM_HERE, base::Bind(&V4L2VideoDecodeAccelerator::InitializeTask,
                             base::Unretained(this)));
 
   return true;
 }
 
+void V4L2VideoDecodeAccelerator::InitializeTask() {
+  DVLOGF(3);
+  DCHECK(decoder_thread_.task_runner()->BelongsToCurrentThread());
+
+  if (!CreateInputBuffers()) {
+    NOTIFY_ERROR(PLATFORM_FAILURE);
+    return;
+  }
+
+  if (!StartDevicePoll())

[Owen Lin, 2016/11/24 07:44:23]

Add a comment that StartDevicePoll with NOTIFY_ERROR, 

[wuchengli, 2016/11/24 08:20:09]

Two other StartDevicePoll doesn't have this comment. I'll keep the code as is to
be consistent.

+    return;
+
+  decoder_state_ = kInitialized;
+}
+
 void V4L2VideoDecodeAccelerator::Decode(
     const BitstreamBuffer& bitstream_buffer) {
   DVLOGF(1) << "input_id=" << bitstream_buffer.id()
             << ", size=" << bitstream_buffer.size();
   DCHECK(decode_task_runner_->BelongsToCurrentThread());
 
   if (bitstream_buffer.id() < 0) {
     LOGF(ERROR) << "Invalid bitstream_buffer, id: " << bitstream_buffer.id();
     if (base::SharedMemory::IsHandleValid(bitstream_buffer.handle()))
       base::SharedMemory::CloseHandle(bitstream_buffer.handle());
@@ skipping 1803 matching lines @@
     DLOGF(ERROR) << "Unexpected visible rectangle " << rect.ToString()
                  << ", top-left is not origin";
     return coded_size;
   }
 
   return rect.size();
 }
 
 bool V4L2VideoDecodeAccelerator::CreateInputBuffers() {
   DVLOGF(3);
+  DCHECK(decoder_thread_.task_runner()->BelongsToCurrentThread());
   // We always run this as we prepare to initialize.
   DCHECK_EQ(decoder_state_, kUninitialized);
   DCHECK(!input_streamon_);
   DCHECK(input_buffer_map_.empty());
 
   struct v4l2_requestbuffers reqbufs;
   memset(&reqbufs, 0, sizeof(reqbufs));
   reqbufs.count = kInputBufferCount;
   reqbufs.type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
   reqbufs.memory = V4L2_MEMORY_MMAP;
@@ skipping 482 matching lines @@
       StartResolutionChange();
   }
 }
 
 void V4L2VideoDecodeAccelerator::ImageProcessorError() {
   LOGF(ERROR) << "Image processor error";
   NOTIFY_ERROR(PLATFORM_FAILURE);
 }
 
 }  // namespace media