In an earlier post I mentioned that one goal of the new introductory curriculum at Carnegie Mellon is to teach parallelism as the general case of computing, rather than an esoteric, specialized subject for advanced students. Many people are incredulous when I tell them this, because it immediately conjures in their mind the myriad complexities…
I recently diagnosed the root cause of a concurrency bug, CR6822370,
and thought it sufficiently interesting to share the details. (CR 6822370 actually represents a
cluster of bugs that are now thought to be related by a common underlying issue).
Briefly, we have a lost wakeup bug in the native C++ Parker::park() platform-specific
infrastructure code that implements java.util.concurrent.LockSupport.park().
The lost wakeup arises from a race that itself arises because of architectural
reordering that in turn occurs because of missing memory barrier instructions.
The lost wakeup may manifest as various 'hangs' or instances of progress failure.
Think writing a compiler is difficult? It is—unless you use Parrot, a complete compiler construction kit. With Parrot, crafting a new programming language is as easy as authoring a new website.
Program performance is always a concern, even in this era of high-performance hardware. This article, the first in a two-part series, guides you around the many pitfalls associated with benchmarking Java code. Part 2 covers the statistics of benchmarking and offers a framework for performing Java benchmarking. Because almost all new languages are virtual machine-based, the general principles the article describes have broad significance for the programming community at large.
C. Click, G. Tene, and M. Wolf. VEE '05: Proceedings of the 1st ACM/USENIX international conference on Virtual execution environments, page 46--56. New York, NY, USA, ACM, (2005)
K. Barabash, and E. Petrank. ISMM '10: Proceedings of the 2010 international symposium on Memory management, page 1--10. New York, NY, USA, ACM, (2010)
M. Paleczny, C. Vick, and C. Click. JVM'01: Proceedings of the 2001 Symposium on JavaTM Virtual Machine Research and Technology Symposium, page 1--1. Berkeley, CA, USA, USENIX Association, (2001)
C. Click, and M. Paleczny. IR '95: Papers from the 1995 ACM SIGPLAN workshop on Intermediate representations, page 35--49. New York, NY, USA, ACM, (1995)
F. Pizlo, L. Ziarek, and J. Vitek. JTRES '09: Proceedings of the 7th International Workshop on Java Technologies for Real-Time and Embedded Systems, page 110--119. New York, NY, USA, ACM, (2009)
F. Pizlo, L. Ziarek, P. Maj, A. Hosking, E. Blanton, and J. Vitek. PLDI '10: Proceedings of the 2010 ACM SIGPLAN conference on Programming language design and implementation, page 146--159. New York, NY, USA, ACM, (2010)
C. Reynolds. SIGGRAPH '87: Proceedings of the 14th annual conference on Computer graphics and interactive techniques, page 25--34. New York, NY, USA, ACM, (1987)
V. Tipparaju, E. Aprá, W. Yu, and J. Vetter. CF '10: Proceedings of the 7th ACM international conference on Computing frontiers, page 207--216. New York, NY, USA, ACM, (2010)