I have a doubt on how a DBUS calls are synchronised or made safe? This is more of a conceptual question. I know that this situation will not arise in SOCKETs. The consumer gets blocked unless the producer has finished its task - recvfrm and sendfrm() in sockets/pipes. Basically, producer and consumer job is well defined here at the two sides of a socket respectively.
Here is a scenario. Actually, I am using QT-DBUS in my project. However, I think that this is not specific to QT DBUS. This question holds true for any DBUS.
There is a function called - "GetTemperatureValue()" of a class. This class gets registered its service with the DBUS - "GetTemperatureValue()". And "GetTemperatureValue()" is invokable from a DBUS Client. Now, if the value returned by "GetTemperatureValue()" is getting changed periodically. Let's say a timer is changing the temperature value very frequently. If in between the client invokes the call - "GetTemperatureValue()" through a DBUS call, then wouldn't it will get a garbage value. Since there is no protection, the temperature value returned could be corrupted. Is there a need for protection here? If protection is required, how can we do so?
Here is a qt-dbus example also - http://www.tune2wizard.com/linux-qt-signals-and-slots-qt-d-bus/