Add functionality which limits the number of bytes on the network.

webrtc/call/call.cc

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 418 matching lines @@
   transport_send->send_side_cc()->RegisterNetworkObserver(this);
   transport_send_ = std::move(transport_send);
   transport_send_->send_side_cc()->SignalNetworkState(kNetworkDown);
   transport_send_->send_side_cc()->SetBweBitrates(
       config_.bitrate_config.min_bitrate_bps,
       config_.bitrate_config.start_bitrate_bps,
       config_.bitrate_config.max_bitrate_bps);
   call_stats_->RegisterStatsObserver(&receive_side_cc_);
   call_stats_->RegisterStatsObserver(transport_send_->send_side_cc());
 
-  module_process_thread_->Start();
+  // We have to attach the pacer to the pacer thread before starting the
+  // module process thread to avoid a race accessing the process thread
+  // both from the process thread and the pacer thread.
+  pacer_thread_->RegisterModule(transport_send_->send_side_cc()->pacer(),
+                                RTC_FROM_HERE);
+  pacer_thread_->RegisterModule(
+      receive_side_cc_.GetRemoteBitrateEstimator(true), RTC_FROM_HERE);
+  pacer_thread_->Start();
+
   module_process_thread_->RegisterModule(call_stats_.get(), RTC_FROM_HERE);
   module_process_thread_->RegisterModule(&receive_side_cc_, RTC_FROM_HERE);
   module_process_thread_->RegisterModule(transport_send_->send_side_cc(),
                                          RTC_FROM_HERE);
-  pacer_thread_->RegisterModule(transport_send_->send_side_cc()->pacer(),
-                                RTC_FROM_HERE);
-  pacer_thread_->RegisterModule(
-      receive_side_cc_.GetRemoteBitrateEstimator(true), RTC_FROM_HERE);
-
-  pacer_thread_->Start();
+  module_process_thread_->Start();
 }
 
 Call::~Call() {
   RTC_DCHECK_RUN_ON(&configuration_thread_checker_);
 
   RTC_CHECK(audio_send_ssrcs_.empty());
   RTC_CHECK(video_send_ssrcs_.empty());
   RTC_CHECK(video_send_streams_.empty());
   RTC_CHECK(audio_receive_streams_.empty());
   RTC_CHECK(video_receive_streams_.empty());
 
+  // The send-side congestion controller must be de-registered prior to
+  // the pacer thread being stopped to avoid a race when accessing the
+  // pacer thread object on the module process thread at the same time as
+  // the pacer thread is stopped.
+  module_process_thread_->DeRegisterModule(transport_send_->send_side_cc());
   pacer_thread_->Stop();
   pacer_thread_->DeRegisterModule(transport_send_->send_side_cc()->pacer());
   pacer_thread_->DeRegisterModule(
       receive_side_cc_.GetRemoteBitrateEstimator(true));
-  module_process_thread_->DeRegisterModule(transport_send_->send_side_cc());
   module_process_thread_->DeRegisterModule(&receive_side_cc_);
   module_process_thread_->DeRegisterModule(call_stats_.get());
   module_process_thread_->Stop();
   call_stats_->DeregisterStatsObserver(&receive_side_cc_);
   call_stats_->DeregisterStatsObserver(transport_send_->send_side_cc());
 
   int64_t first_sent_packet_ms =
       transport_send_->send_side_cc()->GetFirstPacketTimeMs();
   // Only update histograms after process threads have been shut down, so that
   // they won't try to concurrently update stats.
@@ skipping 941 matching lines @@
       (use_send_side_bwe && header.extension.hasTransportSequenceNumber)) {
     receive_side_cc_.OnReceivedPacket(
         packet.arrival_time_ms(), packet.payload_size() + packet.padding_size(),
         header);
   }
 }
 
 }  // namespace internal
 
 }  // namespace webrtc