Communications of the ACM
Making Parallel Programs Reliable with Stable Multithreading
Credit: Joel Ormsby
Reliable software has long been the dream of most researchers, practitioners, and users. In the past decade or so, several research and engineering breakthroughs have greatly improved the reliability of sequential programs (or the sequential aspect of parallel programs); successful examples include Coverity's source code analyzer,6 Microsoft's Static Driver Verifier,3 Valgrind memory checker,17 and certified operating systems and compilers.20
However, the same level of success has not yet propagated to parallel programs, which are notoriously difficult to write, test, analyze, debug, and verify, much more so than the sequential versions. Experts consider reliable parallelism "something of a black art"8 and one of the grand challenges in computing.1,18 But widespread parallel programs are plagued with insidious concurrency bugs15 (such as data races, including concurrent accesses to the same memory location with at least one write, and deadlocks, including threads circularly waiting for resources). Some of the worst of them killed people in the Therac-25 radiation-therapy incidents by generating massive overdoses of radiation and caused the Northeast power blackout of 2003. These bugs can be exploited by attackers violating confidentiality, integrity, and availability of critical systems.24
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