Optimization of a General Model Checking Framework for Various Memory Consistency Models

Abstract

While relaxed memory consistency models contribute optimizations of compilers on multicore CPUs and shared memory distributed programming languages, their relaxedness makes it difficult to write programs correctly. To address this problem, the authors proposed a general model checking framework and implemented a prototype tool McSPIN, which can take a memory consistent model as an input, as well as a program and a property to be checked, in their previous works. However, one big problem of McSPIN was that it was prone to suffer from the state explosion problem, and difficult to be applied to programs other than small example programs. In this paper, we propose optimization approaches for McSPIN to largely reduce the number of state transitions to be explored during model checking so that it can be applied to larger programs. In addition, we actually implemented the optimizations to McSPIN, and this paper gives several experimental results with the optimized McSPIN to show effectiveness of the proposed optimization approaches.

Concurrent Program Logic for Relaxed Memory Consistency Models with Dependencies across Loop Iterations

“…Therefore, our logic cannot currently verify programs that show different orders of effects to different threads, for example, Independent-Reads-IndependentWrite [10]. The authors' previous works on model checking [2], [3], [5] handled such memory consistency models by introducing a notion of visibility of effects on each thread. We think that verification of the program is possible by introducing multilayered store buffers in operational semantics and auxiliary variables that represent variable on the buffers in concurrent program logic.…”

“…The second is to support relaxed memory consistency models (e.g., UPC memory model [43] and C11/C++11 memory models [22], [24]) that do not assume global time. The authors' previous works on model checking [2], [3], [5] handled such memory consistency models by introducing a notion of speculative behavior on each thread. We think that the operational semantics and concurrent program logic can be extended in a similar way.…”

“…To address this problem, program verification can be used to detect bugs caused by unexpected behavior in the relaxed memory consistency models. Recently, program verification for relaxed memory consistency models has been ex- tosh@stair.center tensively studied [1], [2], [3], [5], [7], [8], [9], [11], [14], [25], [35], [40], [49].…”

Reducing State Explosion for Software Model Checking with Relaxed Memory Consistency Models

“…A guard that is uniformly generated as end o==0 from an operation o in Sect. 2.4 is enhanced by an input MCM (details are provided in [3]). We explain this using the constraint that differentiates TSO and PSO, as set out in Sect.…”

“…Although the optimization in our earlier work have enabled verification of non-toy programs such as Dekker's mutual exclusion algorithm [3], it was difficult to apply Mc-SPIN to larger problems such as verifications of copying protocols of Concurrent Copying Garbage Collection algorithms (CCGCs), due to the state explosion. In this paper, we demonstrated the optimizations above enables McSPIN to verify larger programs; we checked if a desirable property of CCGCs, "in a single thread program, what the program reads is what it has most recently written", are held or not for several CCGCs on multiple MCMs.…”