Mojo: Armed Watchers

mojo/edk/system/message_pipe_dispatcher.cc

 // Copyright 2015 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 "mojo/edk/system/message_pipe_dispatcher.h"
 
 #include <limits>
 #include <memory>
 
 #include "base/logging.h"
@@ skipping 146 matching lines @@
 
 #endif  // DCHECK_IS_ON()
 
 MessagePipeDispatcher::MessagePipeDispatcher(NodeController* node_controller,
                                              const ports::PortRef& port,
                                              uint64_t pipe_id,
                                              int endpoint)
     : node_controller_(node_controller),
       port_(port),
       pipe_id_(pipe_id),
-      endpoint_(endpoint) {
+      endpoint_(endpoint),
+      watchers_(this) {
   DVLOG(2) << "Creating new MessagePipeDispatcher for port " << port.name()
            << " [pipe_id=" << pipe_id << "; endpoint=" << endpoint << "]";
 
   node_controller_->SetPortObserver(
       port_,
       make_scoped_refptr(new PortObserverThunk(this)));
 }
 
 bool MessagePipeDispatcher::Fuse(MessagePipeDispatcher* other) {
   node_controller_->SetPortObserver(port_, nullptr);
   node_controller_->SetPortObserver(other->port_, nullptr);
 
   ports::PortRef port0;
   {
     base::AutoLock lock(signal_lock_);
     port0 = port_;
     port_closed_.Set(true);
     awakables_.CancelAll();
+    watchers_.NotifyClosed();
   }
 
   ports::PortRef port1;
   {
     base::AutoLock lock(other->signal_lock_);
     port1 = other->port_;
     other->port_closed_.Set(true);
     other->awakables_.CancelAll();
+    other->watchers_.NotifyClosed();
   }
 
   // Both ports are always closed by this call.
   int rv = node_controller_->MergeLocalPorts(port0, port1);
   return rv == ports::OK;
 }
 
 Dispatcher::Type MessagePipeDispatcher::GetType() const {
   return Type::MESSAGE_PIPE;
 }
 
 MojoResult MessagePipeDispatcher::Close() {
   base::AutoLock lock(signal_lock_);
   DVLOG(2) << "Closing message pipe " << pipe_id_ << " endpoint " << endpoint_
            << " [port=" << port_.name() << "]";
   return CloseNoLock();
 }
 
-MojoResult MessagePipeDispatcher::Watch(MojoHandleSignals signals,
-                                        const Watcher::WatchCallback& callback,
-                                        uintptr_t context) {
-  base::AutoLock lock(signal_lock_);
-
-  if (port_closed_ || in_transit_)
-    return MOJO_RESULT_INVALID_ARGUMENT;
-
-  return awakables_.AddWatcher(
-      signals, callback, context, GetHandleSignalsStateNoLock());
-}
-
-MojoResult MessagePipeDispatcher::CancelWatch(uintptr_t context) {
-  base::AutoLock lock(signal_lock_);
-
-  if (port_closed_ || in_transit_)
-    return MOJO_RESULT_INVALID_ARGUMENT;
-
-  return awakables_.RemoveWatcher(context);
-}
-
 MojoResult MessagePipeDispatcher::WriteMessage(
     std::unique_ptr<MessageForTransit> message,
     MojoWriteMessageFlags flags) {
   if (port_closed_ || in_transit_)
     return MOJO_RESULT_INVALID_ARGUMENT;
 
   size_t num_bytes = message->num_bytes();
   int rv = node_controller_->SendMessage(port_, message->TakePortsMessage());
 
   DVLOG(4) << "Sent message on pipe " << pipe_id_ << " endpoint " << endpoint_
@@ skipping 49 matching lines @@
   if (rv != ports::OK && rv != ports::ERROR_PORT_PEER_CLOSED) {
     if (rv == ports::ERROR_PORT_UNKNOWN ||
         rv == ports::ERROR_PORT_STATE_UNEXPECTED)
       return MOJO_RESULT_INVALID_ARGUMENT;
 
     NOTREACHED();
     return MOJO_RESULT_UNKNOWN;  // TODO: Add a better error code here?
   }
 
   if (no_space) {
+    if (may_discard) {
+      // May have been the last message on the pipe. Need to update signals just
+      // in case.
+      base::AutoLock lock(signal_lock_);
+      watchers_.NotifyState(GetHandleSignalsStateNoLock());
+    }
     // |*num_handles| (and/or |*num_bytes| if |read_any_size| is false) wasn't
     // sufficient to hold this message's data. The message will still be in
     // queue unless MOJO_READ_MESSAGE_FLAG_MAY_DISCARD was set.
     return MOJO_RESULT_RESOURCE_EXHAUSTED;
   }
 
   if (!ports_message) {
     // No message was available in queue.
 
     if (rv == ports::OK)
       return MOJO_RESULT_SHOULD_WAIT;
 
     // Peer is closed and there are no more messages to read.
     DCHECK_EQ(rv, ports::ERROR_PORT_PEER_CLOSED);
     return MOJO_RESULT_FAILED_PRECONDITION;
   }
 
   // Alright! We have a message and the caller has provided sufficient storage
   // in which to receive it.
 
+  {
+    // We need to update anyone watching our signals in case that was the last
+    // available message.
+    base::AutoLock lock(signal_lock_);
+    watchers_.NotifyState(GetHandleSignalsStateNoLock());
+  }
+
   std::unique_ptr<PortsMessage> msg(
       static_cast<PortsMessage*>(ports_message.release()));
 
   const MessageHeader* header =
       static_cast<const MessageHeader*>(msg->payload_bytes());
   const DispatcherHeader* dispatcher_headers =
       reinterpret_cast<const DispatcherHeader*>(header + 1);
 
   if (header->num_dispatchers > std::numeric_limits<uint16_t>::max())
     return MOJO_RESULT_UNKNOWN;
@@ skipping 57 matching lines @@
   *message = MessageForTransit::WrapPortsMessage(std::move(msg));
   return MOJO_RESULT_OK;
 }
 
 HandleSignalsState
 MessagePipeDispatcher::GetHandleSignalsState() const {
   base::AutoLock lock(signal_lock_);
   return GetHandleSignalsStateNoLock();
 }
 
+MojoResult MessagePipeDispatcher::AddWatcherRef(
+    const scoped_refptr<WatcherDispatcher>& watcher,
+    uintptr_t context) {
+  base::AutoLock lock(signal_lock_);
+  if (port_closed_ || in_transit_)
+    return MOJO_RESULT_INVALID_ARGUMENT;
+  return watchers_.Add(watcher, context, GetHandleSignalsStateNoLock());
+}
+
+MojoResult MessagePipeDispatcher::RemoveWatcherRef(WatcherDispatcher* watcher,
+                                                   uintptr_t context) {
+  base::AutoLock lock(signal_lock_);
+  if (port_closed_ || in_transit_)
+    return MOJO_RESULT_INVALID_ARGUMENT;
+  return watchers_.Remove(watcher, context);
+}
+
 MojoResult MessagePipeDispatcher::AddAwakable(
     Awakable* awakable,
     MojoHandleSignals signals,
     uintptr_t context,
     HandleSignalsState* signals_state) {
   base::AutoLock lock(signal_lock_);
 
   if (port_closed_ || in_transit_) {
     if (signals_state)
       *signals_state = HandleSignalsState();
@@ skipping 80 matching lines @@
   port_transferred_ = true;
   in_transit_.Set(false);
   CloseNoLock();
 }
 
 void MessagePipeDispatcher::CancelTransit() {
   base::AutoLock lock(signal_lock_);
   in_transit_.Set(false);
 
   // Something may have happened while we were waiting for potential transit.
-  awakables_.AwakeForStateChange(GetHandleSignalsStateNoLock());
+  HandleSignalsState state = GetHandleSignalsStateNoLock();
+  awakables_.AwakeForStateChange(state);
+  watchers_.NotifyState(state);
 }
 
 // static
 scoped_refptr<Dispatcher> MessagePipeDispatcher::Deserialize(
     const void* data,
     size_t num_bytes,
     const ports::PortName* ports,
     size_t num_ports,
     PlatformHandle* handles,
     size_t num_handles) {
@@ skipping 15 matching lines @@
   DCHECK(port_closed_ && !in_transit_);
 }
 
 MojoResult MessagePipeDispatcher::CloseNoLock() {
   signal_lock_.AssertAcquired();
   if (port_closed_ || in_transit_)
     return MOJO_RESULT_INVALID_ARGUMENT;
 
   port_closed_.Set(true);
   awakables_.CancelAll();
+  watchers_.NotifyClosed();
 
   if (!port_transferred_) {
     base::AutoUnlock unlock(signal_lock_);
     node_controller_->ClosePort(port_);
   }
 
   return MOJO_RESULT_OK;
 }
 
 HandleSignalsState MessagePipeDispatcher::GetHandleSignalsStateNoLock() const {
@@ skipping 44 matching lines @@
                << " endpoint " << endpoint_ << " [port=" << port_.name()
                << "; size=" << filter.message_size() << "]";
     }
     if (port_status.peer_closed) {
       DVLOG(2) << "Peer closure detected on message pipe " << pipe_id_
                << " endpoint " << endpoint_ << " [port=" << port_.name() << "]";
     }
   }
 #endif
 
-  awakables_.AwakeForStateChange(GetHandleSignalsStateNoLock());
+  HandleSignalsState state = GetHandleSignalsStateNoLock();
+  awakables_.AwakeForStateChange(state);
+  watchers_.NotifyState(state);
 }
 
 }  // namespace edk
 }  // namespace mojo