COMP 3000 Essay 2 2010 Question 7

Paper

Ad Hoc Synchronization Considered Harmful

Weiwei Xiong University of California, San Diego

Soyeon Park, Jiaqi Zhang, Yuanyuan Zhou University of Illinois at Urbana-Champaign

Zhiqiang Ma Intel

Research Problem

As the computer industry continues to shift towards multicore processors, concurrent programming and the use of multithreaded designs has increased to keep up with this growing trend. Multithreaded applications can be found in a variety of popular applications today as they take advantage of the multithreaded approach. However, the concepts behind concurrent programming bring with them a host of potential dangers in the form of race conditions and deadlocks resulting from bad programming design and threads accessing shared memory. Fortunately, there are well known and standard methods for dealing with these problems, i.e synchronization primitives. But in real world situations, due to a variety of reasons, as we shall see, programmers often implement their own "ad hoc" synchronizations that eschew common design standards. Ad hoc synchronizations are not well documented and are not discovered by traditional tools for race conditions that look for standard synchronization primitives.

This paper addresses these concerns in two regards, first it details a thorough study of ad hoc synchronizations. It details their nature, dangers, impact on bug detection tools and prevalence in several major open-source applications. Secondly, it introduces SyncFinder, a program that detects all ad hoc synchronizations and automatically annotates the source code where ad hoc sychnronizations are found. This can see use in conjunction with other data race checkers to improve accuracy and to build custom tools for finding deadlocks and bad programming practices.

With detailed analysis of ad hoc synchronization and study of their occurrences in several applications, the research ultimately concludes that they are harmful and should be removed. At the same time, SyncFinder detects and documents ad hoc synchronizations in the source code enabling programmers for the first time to easily track and remove them.

Contribution

Intro to the study of the major applications and what they found

Findings

1.they are prevalent, all applications had them

2. hard to find

3. error prone

4.effect other bug detection

5. They are diverse. Different forms, multiple exits and dependencies

Reasons behind why people use ad hoc synchronization and possible improvements over them ie Synchronization primitives

SyncFinder

Intro to what it is and what it does

How it works

1. find loops

2. identify sync loops

3. EDV analysis

4. Pruning

5. Annotation of found sync

Uses

1. A tool to detect bad practices

2. Extensions to data race detection

Critique

1. Uses static approach, dynamic would be better

2. not entirely accurate, some false positives.

Example footnote¹

References

¹ Author, 2010. Title. [online] Company(optional) Available at: <http://www.google.com> [Accessed 13 October 2010].