@article{qiu_shao_zhao_khan_hui_jin_2022, title={A Deep Study of the Effects and Fixes of Server-Side Request Races in Web Applications}, ISSN={["2160-1852"]}, DOI={10.1145/3524842.3528463}, abstractNote={Server-side web applications are vulnerable to request races. While some previous studies of real-world request races exist, they primarily focus on the root cause of these bugs. To better combat request races in server-side web applications, we need a deep understanding of their characteristics. In this paper, we provide a complementary focus on race effects and fixes with an enlarged set of request races from web applications developed with Object-Relational Mapping (ORM) frameworks. We revisit characterization questions used in previous studies on newly included request races, distinguish the external and internal effects of request races, and relate requestrace fixes with concurrency control mechanisms in languages and frameworks for developing server-side web applications. Our study reveals that: (1) request races from ORM-based web applications share the same characteristics as those from raw-SQL web applications; (2) request races violating application semantics without explicit crashes and error messages externally are common, and latent request races, which only corrupt some shared resource internally but require extra requests to expose the misbehavior, are also common; and (3) various fix strategies other than using synchronization mechanisms are used to fix request races. We expect that our results can help developers better understand request races and guide the design and development of tools for combating request races.}, journal={2022 MINING SOFTWARE REPOSITORIES CONFERENCE (MSR 2022)}, author={Qiu, Zhengyi and Shao, Shudi and Zhao, Qi and Khan, Hassan Ali and Hui, Xinning and Jin, Guoliang}, year={2022}, pages={744–756} }
 @article{zhao_qiu_shao_hui_khan_jin_2022, title={Understanding and Reaching the Performance Limit of Schedule Tuning on Stable Synchronization Determinism}, DOI={10.1145/3559009.3569669}, abstractNote={Deterministic MultiThreading (DMT) systems eliminate nondeterminism from the dynamic executions of multithreaded programs. They can greatly simplify multithreaded programming and ease the deployment of systems that rely on replication. We first categorize and compare existing DMT system designs along three axes, incorporating the most recent advances in DMT systems. From our study, we conclude that stable synchronization determinism is the most cost-effective design, and it is thus the focus of our work. To reduce the overhead of enforcing stable synchronization determinism, previous work has explored scheduling-based methods that tune the synchronization schedule. However, it is not clear how low the performance overhead can be through schedule tuning and how to reach the performance limit. To answer these questions, we then follow an iterative process of understanding the performance limit of schedule tuning on stable synchronization determinism and designing new scheduling policies to reach the performance limit. Through this process, we identify two types of scheduling-oblivious overheads that cannot be eliminated by schedule tuning alone. In addition, we also design a group of new policies and implement them in minSMT. Our evaluation shows that minSMT successfully reaches the performance limit of stable synchronization determinism on 107 out of 108 benchmarks after excluding the impact of scheduling-oblivious overheads, and this also results in significant performance improvements compared with state-of-the-art stable synchronization-determinism systems on 9 benchmarks. Our results also suggest that, to further improve the performance of stable synchronization determinism, future research should focus on addressing the two types of scheduling-oblivious overheads with approaches other than schedule tuning.}, journal={PROCEEDINGS OF THE 2022 31ST INTERNATIONAL CONFERENCE ON PARALLEL ARCHITECTURES AND COMPILATION TECHNIQUES, PACT 2022}, author={Zhao, Qi and Qiu, Zhengyi and Shao, Shudi and Hui, Xinning and Khan, Hassan Ali and Jin, Guoliang}, year={2022}, pages={223–238} }