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UBC Theses and Dissertations

Dynamic race detection for non-coherent accelerators Young, May


Modern System-on-Chip (SoC) designs are increasingly complex and heterogeneous, featuring specialized hardware accelerators and processor cores that access shared memory. Non-coherent accelerators are one common memory coherence model. The advantage of non-coherence in accelerators is that it cut costs on extra hardware that would have been used for memory coherence. However, the disadvantage is that the programmer must know where and when to synchronize between the accelerator and the processor. Getting this synchronization correct can be difficult. We propose a novel approach to find data races in software for non-coherent accelerators in heterogeneous systems. The intuition underlying our approach is that a sufficiently precise abstraction of the hardware's behaviour is straightforward to derive, based on common idioms for memory access. To demonstrate this, we derived simple rules and axioms to model the interaction between a processor and a massively parallel accelerator provided by a commercial FPGA-based accelerator vendor. We implemented these rules in a prototype tool for dynamic race detection, and performed experiments on eleven examples provided by the vendor. The tool is able to detect previously unknown races in two of the eleven examples, and additional races if we introduce bugs in the synchronization in the code.

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