Detecting deadlock automatically? (New paper)
To verify sequential programs, we have to prove that they do the right thing, but also that they do it within our lifetime — that they terminate. The termination problem is considerably harder with concurrent programs, since they add a new form of non-termination: deadlock. A set of concurrent processes or threads will deadlock if they end up each holding a resource that another wants and wanting a resource that another holds.
There is no general solution to the deadlock problem, even a good enough general solution. (“Good enough” is the best we can hope for, since like many important problems deadlock is undecidable.) It is already hard enough to provide run-time deadlock detection, to be able at least to cancel execution when deadlock happens. The research reported in this new paper [1] pursues the harder goal of static detection. It applies to an object-oriented context (specifically the SCOOP model of concurrent OO computation) and relies fundamentally on the alias calculus, a static alias analysis technique developed in previous publications.
The approach is at its inception and considerable work remains to be done. Still, the example handled by the paper is encouraging: analyzing two versions of the dining philosophers problem and proving — manually — that one can deadlock and the other cannot.
References
[1] Bertrand Meyer: An automatic technique for static deadlock prevention, in PSI 2014 (Ershov Informatics Conference), eds. Irina Virbitskaite and Andrei Voronkov, Lecture Notes in Computer Science, Springer, 2015, to appear.; draft available here.
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