cashew: defer all D-Bus signal processing to main loop

src/device.cc

Index: src/device.cc
diff --git a/src/device.cc b/src/device.cc
index abcc781d984dbaf83a741a52a3c5eef24ef6269c..b5ac6f5103d8a1c05e82b0f6633d7bd6b965b6a0 100644
--- a/src/device.cc
+++ b/src/device.cc
@@ -47,6 +47,7 @@ Device::Device(Service * const parent, DBus::Connection& connection,  // NOLINT
   if (get_properties_source_id_ == 0) {
     LOG(ERROR) << path_ << ": ctor: g_idle_add failed";
   }
+  property_changed_handler_.delegate(this);
 }
 
 Device::~Device() {
@@ -78,6 +79,21 @@ const std::string& Device::GetInterface() const {
 void Device::PropertyChanged(const std::string& property_name,
                              const DBus::Variant& new_value) {
   DLOG(INFO) << path_ << ": PropertyChanged: property_name = " << property_name;
+  // Queue a tuple representing this signal for later processing from the glib
+  // main loop. We do this to avoid libdbus-c++ deadlocks that can occur when
+  // sending a dbus message from within a dbus callback like this one.
+  PropertyChangedSignal signal(property_name, new_value);
+  property_changed_handler_.EnqueueSignal(signal);
+}
+
+// PropertyChangedDelegate methods
+
+void Device::OnPropertyChanged(const PropertyChangedHandler *handler,
+                               const std::string& property_name,
+                               const DBus::Variant& new_value) {
+  DCHECK(handler == &property_changed_handler_);
+  DLOG(INFO) << path_ << ": OnPropertyChanged: property_name = "
+      << property_name;
   if (property_name == kFlimflamDeviceCarrierProperty) {
     OnCarrierUpdate(new_value.reader().get_string());
   } else if (property_name == kFlimflamDeviceInterfaceProperty) {