Never lock the Pepper proxy lock on the IO thread

content/ppapi_plugin/ppapi_thread.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 "content/ppapi_plugin/ppapi_thread.h"
 
 #include <limits>
 
 #include "base/command_line.h"
 #include "base/cpu.h"
@@ skipping 95 matching lines @@
       next_plugin_dispatcher_id_(1) {
   ppapi::proxy::PluginGlobals* globals = ppapi::proxy::PluginGlobals::Get();
   globals->SetPluginProxyDelegate(this);
   globals->set_command_line(
       command_line.GetSwitchValueASCII(switches::kPpapiFlashArgs));
 
   blink_platform_impl_.reset(new PpapiBlinkPlatformImpl);
   blink::initialize(blink_platform_impl_.get());
 
   if (!is_broker_) {
-    channel()->AddFilter(
+    scoped_refptr<ppapi::proxy::PluginMessageFilter> plugin_filter(
         new ppapi::proxy::PluginMessageFilter(
             NULL, globals->resource_reply_thread_registrar()));
+    channel()->AddFilter(plugin_filter.get());
+    globals->RegisterResourceMessageFilters(plugin_filter.get());

[raymes, 2015/03/03 03:07:44]

I guess both these add references?

[dmichael (off chromium), 2015/03/03 18:27:56]

This is a little confusing, and I struggled with how to organize this and name
stuff.

As it's organized in this patch, PluginGlobals knows about any special
plugin-side filters that need to be able to listen on the IO thread. In this
case, that's only UDPSocketFilter. There needs to be exactly one instance of
UDPSocketFilter, and it must be accessible from two places:
- UDPSocketResourceBase (for adding/removing itself and draining its message
queue)
- PluginMessageFilter has to be able to pass messages to it.

I chose to make PluginMessageFilter have no special knowledge about what
particular plugin filters there are. Instead, it asks PluginGlobals to add all
the filters that PluginGlobals knows about (see the implementation of
RegisterResourceMessageFilters).

So effectively, this is adding UDPSocketFilter to PluginMessageFilter's list of
ResourceMessageFilters.

PluginGlobals will not have a reference on PluginMessageFilter. On the other
hand, PluginMessageFilter and PluginGlobals *will* both have a reference on
UDPSocketFilter (maybe that's what you meant) 

   }
 }
 
 PpapiThread::~PpapiThread() {
 }
 
 void PpapiThread::Shutdown() {
   ChildThreadImpl::Shutdown();
 
   ppapi::proxy::PluginGlobals::Get()->ResetPluginProxyDelegate();
@@ skipping 417 matching lines @@
       std::string("Plugin.Ppapi") + (is_broker_ ? "Broker" : "Plugin") +
       "LoadErrorCode_" + path.BaseName().MaybeAsASCII();
 
   // For sparse histograms, we can use the macro, as it does not incorporate a
   // static.
   UMA_HISTOGRAM_SPARSE_SLOWLY(histogram_name, error.code);
 #endif
 }
 
 }  // namespace content