Add a thread-safe CreateChannel method to ChannelManager.

mojo/edk/system/channel_manager.h

 // 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.
 
 #ifndef MOJO_EDK_SYSTEM_CHANNEL_MANAGER_H_
 #define MOJO_EDK_SYSTEM_CHANNEL_MANAGER_H_
 
 #include <stdint.h>
 
 #include "base/containers/hash_tables.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
-#include "base/task_runner.h"
 #include "mojo/edk/embedder/scoped_platform_handle.h"
 #include "mojo/edk/system/channel.h"
 #include "mojo/edk/system/channel_info.h"
 
+namespace base {
+class TaskRunner;
+}
+
 namespace mojo {
 
 namespace embedder {
 class PlatformSupport;
 }
 
 namespace system {
 
 // IDs for |Channel|s managed by a |ChannelManager|. (IDs should be thought of
 // as specific to a given |ChannelManager|.) 0 is never a valid ID.
@@ skipping 10 matching lines @@
   explicit ChannelManager(embedder::PlatformSupport* platform_support);
   ~ChannelManager();
 
   // Creates a |Channel| and adds it to the set of channels managed by this
   // |ChannelManager|. |channel_id| should be a valid |ChannelId| (i.e.,
   // nonzero) not "assigned" to any other |Channel| being managed by this
   // |ChannelManager|.
   // TODO(vtl): Currently, this should be called on any I/O thread (which will
   // become the new channel's "channel thread"). Eventually, the channel manager
   // will have an assigned I/O thread, on which this must be called.
-  // TODO(vtl): Maybe this should return a message pipe dispatcher (for the
+  // TODO(vtl): Probably this should return a message pipe dispatcher (for the
   // bootstrap message pipe) instead.
   void CreateChannelOnIOThread(
       ChannelId channel_id,
       embedder::ScopedPlatformHandle platform_handle,
       scoped_refptr<system::ChannelEndpoint> bootstrap_channel_endpoint);
 
+  // Like |CreateChannelOnIOThread()|, but may be called from any thread. On
+  // completion, will call |callback| ("on" |io_thread_task_runner| if
+  // |callback_thread_task_runner| is null else by posting to using

[yzshen1, 2015/02/04 21:21:06]

nit: using is not needed.

+  // |callback_thread_task_runner|). Note: This will always post a task to the
+  // I/O thread, even if |io_thread_task_runner| is the task runner for the
+  // current thread.
+  // TODO(vtl): The |io_thread_task_runner| argument is temporary (we should use
+  // the channel manager's I/O thread).
+  // TODO(vtl): Probably this should return a message pipe dispatcher (for the
+  // bootstrap message pipe) instead.
+  void CreateChannel(
+      ChannelId channel_id,
+      embedder::ScopedPlatformHandle platform_handle,
+      scoped_refptr<system::ChannelEndpoint> bootstrap_channel_endpoint,
+      scoped_refptr<base::TaskRunner> io_thread_task_runner,
+      base::Closure callback,
+      scoped_refptr<base::TaskRunner> callback_thread_task_runner);
+
   // Gets the |Channel| with the given ID (which must exist).
   scoped_refptr<Channel> GetChannel(ChannelId channel_id) const;
 
   // Informs the channel manager (and thus channel) that it will be shutdown
   // soon (by calling |ShutdownChannel()|). Calling this is optional (and may in
   // fact be called multiple times) but it will suppress certain warnings (e.g.,
   // for the channel being broken) and enable others (if messages are written to
   // the channel).
   void WillShutdownChannel(ChannelId channel_id);
 
   // Shuts down the channel specified by the given ID. It is up to the caller to
   // guarantee that this is only called once per channel (that was added using
   // |CreateChannelOnIOThread()|). If called from the channel's creation thread
   // (i.e., |base::MessageLoopProxy::current()| is the channel thread's
   // |TaskRunner|), this will complete synchronously.
   void ShutdownChannel(ChannelId channel_id);
 
  private:
+  void CreateChannelHelper(
+      ChannelId channel_id,
+      embedder::ScopedPlatformHandle platform_handle,
+      scoped_refptr<system::ChannelEndpoint> bootstrap_channel_endpoint,
+      base::Closure callback,
+      scoped_refptr<base::TaskRunner> callback_thread_task_runner);
+
   embedder::PlatformSupport* const platform_support_;
 
   // Note: |Channel| methods should not be called under |lock_|.
   mutable base::Lock lock_;  // Protects the members below.
 
   // TODO(vtl): Once we give the |ChannelManager| one single I/O thread, we can
   // get rid of |ChannelInfo| (and just have ref pointers to |Channel|s).
   base::hash_map<ChannelId, ChannelInfo> channel_infos_;
 
   DISALLOW_COPY_AND_ASSIGN(ChannelManager);
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_CHANNEL_MANAGER_H_