Model checking copy phases of concurrent copying garbage collection with various memory models

Abstract

Modern concurrent copying garbage collection (GC), in particular, real-time GC, uses fine-grained synchronizations with a mutator, which is the application program that mutates memory, when it moves objects in its copy phase. It resolves a data race using a concurrent copying protocol, which is implemented as interactions between the collector threads and the read and write barriers that the mutator threads execute. The behavioral effects of the concurrent copying protocol rely on the memory model of the CPUs and the programming languages in which the GC is implemented. It is difficult, however, to formally investigate the behavioral properties of concurrent copying protocols against various memory models. To address this problem, we studied the feasibility of the bounded model checking of concurrent copying protocols with memory models. We investigated a correctness-related behavioral property of copying protocols of various concurrent copying GC algorithms, including real-time GC Stopless, Clover, Chicken, Staccato, and Schism against six memory models, total store ordering (TSO), partial store ordering (PSO), relaxed memory ordering (RMO), and their variants, in addition to sequential consistency (SC) using bounded model checking. For each combination of a protocol and memory model, we conducted model checking with a model of a mutator. In this wide range of case studies, we found faults in two GC algorithms, one of which is relevant to the memory model. We fixed these faults with the great help of counterexamples. We also modified some protocols so that they work under some memory models weaker than those for which the original protocols were designed, and checked them using model checking. We believe that bounded model checking is a feasible approach to investigate behavioral properties of concurrent copying protocols under weak memory models. CCS Concepts: • Software and its engineering → Garbage collection; Model checking;

Heap Fuzzing: Automatic Garbage Collection Testing with Expert-Guided Random Events

“…One family of solutions performs static verifications of GC algorithms using theorem provers [13], [27]. A second family of solutions implements model checking approaches [5], [29], [34].…”

“…Existing work proposes to perform static verifications of garbage collection (GC) algorithms using theorem This work was funded by Inria -AlaMVic Action Exploratoire provers [13], [27] and model checking [5], [29], [34]. Such approaches are heavy-weight to implement and execute, even at the expense of requiring specific techniques to optimize them [1] (See Section VI).…”

Visualization of Counterexamples of Memory Model-aware Model Checking Using SPIN

“…Staccato uses fence instructions so that it works correctly even if the memory order differs from the program order. However, there is a bug in Staccato: a value written by the mutator may not be copied to the to-space [15].…”

“…From our experience in using memory model-aware model checking for debugging, we identified the following information for each execution step as useful for understanding bugs [5], [15].…”