On Ordering Problems in Message Passing Software

The need for concurrency in modern software is increasingly fulfilled by utilizing the message passing paradigm because of its modularity and scalability. In the message passing paradigm, concurrently running processes communicate by sending and receiving messages. Asynchronous messaging introduces the possibility of message ordering problems: two messages with a specific order in the program text could take effect in the opposite order in the program execution and lead to bugs that are hard to find and debug. We believe that the engineering of message passing software could be easier if more is known about the characteristics of message ordering problems in practice. In this work, we present an analysis to study and quantify the relation between ordering problems and semantics variations of their underlying message passing paradigm in over 30 applications. Some of our findings are as follows: (1) semantic variations of the message passing paradigm can cause ordering problems exhibited by applications in different programming patterns to vary greatly; (2) some semantic features such as in-order messaging are critical for reducing ordering problems; (3) modular enforcement of aliasing in terms of data isolation allows small test configurations to trigger the majority of ordering problems.