Mojo: Implement plumbing to support passing handles over MessagePipes.

This is tricky for several reasons:
  - We have fine-grained locking (and would like to keep it that way),
    and need to avoid deadlock. In particular, acquiring multiple
    dispatcher locks simultaneously is dangerous -- so we allow it to
    fail.
  - We want clean failure semantics. In particular, on failure,
    WriteMessage() should leave the handles being sent valid. This means
    that we may not remove them from the handle table until the call has
    succeeded. Thus we have to mark them as busy.
  - We need to avoid various races. E.g., still to do: When sending a
    handle in-process, it's important that once |WriteMessage()| has
    sent a handle, no more calls done on that particular handle may
    proceed. As a result, we won't be able to simply transfer
    dispatchers to a new handle (in-process) but instead must create a
    new dispatcher referencing the same resource. This will also ensure
    that |Wait()|s on that handle will be properly cancelled.

R=darin@chromium.org, darin

Review URL: https://codereview.chromium.org/67413003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234302 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 8 insertions, 4 deletions

diff --git a/mojo/system/message_pipe.h b/mojo/system/message_pipe.h
index 67f99d2..fc5ec63 100644
--- a/mojo/system/message_pipe.h
+++ b/mojo/system/message_pipe.h
@@ -5,6 +5,8 @@
 #ifndef MOJO_SYSTEM_MESSAGE_PIPE_H_
 #define MOJO_SYSTEM_MESSAGE_PIPE_H_
 
+#include <vector>
+
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
@@ -18,6 +20,7 @@ namespace mojo {
 namespace system {
 
 class Channel;
+class Dispatcher;
 class MessagePipeEndpoint;
 class Waiter;
 
@@ -43,16 +46,17 @@ class MOJO_SYSTEM_EXPORT MessagePipe :
   void CancelAllWaiters(unsigned port);
   void Close(unsigned port);
   // Unlike |MessagePipeDispatcher::WriteMessage()|, this does not validate its
-  // arguments. |bytes|/|num_bytes| and |handles|/|num_handles| must be valid.
+  // arguments.
   MojoResult WriteMessage(unsigned port,
                           const void* bytes, uint32_t num_bytes,
-                          const MojoHandle* handles, uint32_t num_handles,
+                          const std::vector<Dispatcher*>* dispatchers,
                           MojoWriteMessageFlags flags);
   // Unlike |MessagePipeDispatcher::ReadMessage()|, this does not validate its
-  // arguments. |bytes|/|num_bytes| and |handles|/|num_handles| must be valid.
+  // arguments.
   MojoResult ReadMessage(unsigned port,
                          void* bytes, uint32_t* num_bytes,
-                         MojoHandle* handles, uint32_t* num_handles,
+                         uint32_t max_num_dispatchers,
+                         std::vector<scoped_refptr<Dispatcher> >* dispatchers,
                          MojoReadMessageFlags flags);
   MojoResult AddWaiter(unsigned port,
                        Waiter* waiter,