IPC: change sync channel dispatch restriction to allow dispatch to other channels within the same "…

ipc/ipc_sync_channel.h

 // Copyright (c) 2011 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 IPC_IPC_SYNC_CHANNEL_H_
 #define IPC_IPC_SYNC_CHANNEL_H_
 #pragma once
 
 #include <string>
 #include <deque>
@@ skipping 44 matching lines @@
 // be dispatched in a reentrant manner to avoid deadlock.
 //
 //
 // Note that care must be taken that the lifetime of the ipc_thread argument
 // is more than this object.  If the message loop goes away while this object
 // is running and it's used to send a message, then it will use the invalid
 // message loop pointer to proxy it to the ipc thread.
 class IPC_EXPORT SyncChannel : public ChannelProxy,
                                public base::WaitableEventWatcher::Delegate {
  public:
+  enum RestrictDispatchGroup {
+    kRestrictDispatchGroup_None = 0,
+  };
+
   // Creates and initializes a sync channel. If create_pipe_now is specified,
   // the channel will be initialized synchronously.
   SyncChannel(const IPC::ChannelHandle& channel_handle,
               Channel::Mode mode,
               Channel::Listener* listener,
               base::MessageLoopProxy* ipc_message_loop,
               bool create_pipe_now,
               base::WaitableEvent* shutdown_event);
 
   // Creates an uninitialized sync channel. Call ChannelProxy::Init to
   // initialize the channel. This two-step setup allows message filters to be
   // added before any messages are sent or received.
   SyncChannel(Channel::Listener* listener,
               base::MessageLoopProxy* ipc_message_loop,
               base::WaitableEvent* shutdown_event);
 
   virtual ~SyncChannel();
 
   virtual bool Send(Message* message) OVERRIDE;
   virtual bool SendWithTimeout(Message* message, int timeout_ms);
 
   // Whether we allow sending messages with no time-out.
   void set_sync_messages_with_no_timeout_allowed(bool value) {
     sync_messages_with_no_timeout_allowed_ = value;
   }
 
-  // Sets this channel to only dispatch its incoming unblocking messages when it
-  // is itself blocked on sending a sync message, not when other channels are.
+  // Sets the dispatch group for this channel, to only allow re-entrant dispatch
+  // of messages to other channels in the same group.
   //
   // Normally, any unblocking message coming from any channel can be dispatched
   // when any (possibly other) channel is blocked on sending a message. This is
   // needed in some cases to unblock certain loops (e.g. necessary when some
   // processes share a window hierarchy), but may cause re-entrancy issues in
   // some cases where such loops are not possible. This flags allows the tagging
-  // of some particular channels to not re-enter in such cases.
-  void SetRestrictDispatchToSameChannel(bool value);
+  // of some particular channels to only re-enter in known correct cases.
+  //
+  // Incoming messages on channels belonging to a group that is not
+  // kRestrictDispatchGroup_None will only be dispatched while a sync message is
+  // being sent on a channel of the *same* group.
+  // Incoming messages belonging to the kRestrictDispatchGroup_None group (the
+  // default) will be dispatched in any case.
+  void SetRestrictDispatchChannelGroup(int group);
 
  protected:
   class ReceivedSyncMsgQueue;
   friend class ReceivedSyncMsgQueue;
 
   // SyncContext holds the per object data for SyncChannel, so that SyncChannel
   // can be deleted while it's being used in a different thread.  See
   // ChannelProxy::Context for more information.
   class SyncContext : public Context,
                       public base::WaitableEventWatcher::Delegate {
@@ skipping 28 matching lines @@
     // Called on the IPC thread when a sync send that runs a nested message loop
     // times out.
     void OnSendTimeout(int message_id);
 
     base::WaitableEvent* shutdown_event() { return shutdown_event_; }
 
     ReceivedSyncMsgQueue* received_sync_msgs() {
       return received_sync_msgs_;
     }
 
-    void set_restrict_dispatch(bool value) { restrict_dispatch_ = value; }
-    bool restrict_dispatch() const { return restrict_dispatch_; }
+    void set_restrict_dispatch_group(int group) {
+      restrict_dispatch_group_ = group;
+    }
+
+    int restrict_dispatch_group() const {
+      return restrict_dispatch_group_;
+    }
 
    private:
     virtual ~SyncContext();
     // ChannelProxy methods that we override.
 
     // Called on the listener thread.
     virtual void Clear() OVERRIDE;
 
     // Called on the IPC thread.
     virtual bool OnMessageReceived(const Message& msg) OVERRIDE;
     virtual void OnChannelError() OVERRIDE;
     virtual void OnChannelOpened() OVERRIDE;
     virtual void OnChannelClosed() OVERRIDE;
 
     // Cancels all pending Send calls.
     void CancelPendingSends();
 
     // WaitableEventWatcher::Delegate implementation.
     virtual void OnWaitableEventSignaled(base::WaitableEvent* arg) OVERRIDE;
 
     typedef std::deque<PendingSyncMsg> PendingSyncMessageQueue;
     PendingSyncMessageQueue deserializers_;
     base::Lock deserializers_lock_;
 
     scoped_refptr<ReceivedSyncMsgQueue> received_sync_msgs_;
 
     base::WaitableEvent* shutdown_event_;
     base::WaitableEventWatcher shutdown_watcher_;
-    bool restrict_dispatch_;
+    int restrict_dispatch_group_;
   };
 
  private:
   // WaitableEventWatcher::Delegate implementation.
   virtual void OnWaitableEventSignaled(base::WaitableEvent* arg) OVERRIDE;
 
   SyncContext* sync_context() {
     return reinterpret_cast<SyncContext*>(context());
   }
 
@@ skipping 13 matching lines @@
 
   // Used to signal events between the IPC and listener threads.
   base::WaitableEventWatcher dispatch_watcher_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncChannel);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_SYNC_CHANNEL_H_