DCHECK that listener thread != IO thread

ipc/ipc_channel_proxy.cc

 // Copyright (c) 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 "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/debug/trace_event.h"
 #include "base/location.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 127 matching lines @@
 
 ChannelProxy::Context::Context(Listener* listener,
                                base::SingleThreadTaskRunner* ipc_task_runner)
     : listener_task_runner_(base::ThreadTaskRunnerHandle::Get()),
       listener_(listener),
       ipc_task_runner_(ipc_task_runner),
       channel_connected_called_(false),
       message_filter_router_(new MessageFilterRouter()),
       peer_pid_(base::kNullProcessId) {
   DCHECK(ipc_task_runner_.get());
+  // The Listener thread where Messages are handled must be a separate thread
+  // to avoid oversubscribing the IO thread. If you trigger this error, you
+  // need to either:
+  // 1) Create the ChannelProxy on a different thread, or
+  // 2) Just use Channel
+  // Note, we currently make an exception for a NULL listener. That usage
+  // basically works, but is outside the intent of ChannelProxy. This support
+  // will disappear, so please don't rely on it. See crbug.com/364241
+  DCHECK(!listener || (ipc_task_runner_.get() != listener_task_runner_.get()));
 }
 
 ChannelProxy::Context::~Context() {
 }
 
 void ChannelProxy::Context::ClearIPCTaskRunner() {
   ipc_task_runner_ = NULL;
 }
 
 void ChannelProxy::Context::CreateChannel(const IPC::ChannelHandle& handle,
@@ skipping 372 matching lines @@
   Channel* channel = context_.get()->channel_.get();
   // Channel must have been created first.
   DCHECK(channel) << context_.get()->channel_id_;
   return channel->GetPeerEuid(peer_euid);
 }
 #endif
 
 //-----------------------------------------------------------------------------
 
 }  // namespace IPC