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* Add docs: exp-drd/docs/README.txt * Added one drd suppression pattern, and cleaned up the suppression file. * All regression tests now pass on x86_64 and i386, including sigalrm. * Updated TODO.txt file. * pth_create_chain test is now started with 100 threads instead of 10 -- 10 was not enough. * DRD no longer exits on PPC32 and PPC64 but just prints a warning message before it starts. git-svn-id: svn://svn.valgrind.org/valgrind/trunk@7275
84 lines
3.6 KiB
Plaintext
84 lines
3.6 KiB
Plaintext
DRD: a Data Race Detector
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=========================
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Last update: December 3, 2007 by Bart Van Assche.
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The Difficulty of Multithreading Programming
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--------------------------------------------
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Multithreading is a concept to model multiple concurrent activities within a
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single process. Since the invention of the multithreading concept, there is an
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ongoing debate about which way to model concurrent activities is better --
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multithreading or message passing. This debate exists because
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multithreaded programming is error prone: multithreaded programs can exhibit
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data races and/or deadlocks. Despite these risks multithreaded programming is
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popular: for many applications multithreading is a more natural programming
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style, and multithreaded code often runs faster than the same application
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implemented via message passing.
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In the context of DRD, a data race is defined as two concurrent memory
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accesses, where at least one of these two memory accesses is a store operation,
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and these accesses are not protected by proper locking constructs. Data
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races are harmful because these may lead to unpredictable results in
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multithreaded programs. There is a general consensus that data races
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should be avoided in multithreaded programs.
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About DRD
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---------
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The current version of DRD is able to perform data race detection on small
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programs -- DRD quickly runs out of memory for realistically sized programs.
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The current version runs well under Linux on x86 CPU's for multithreaded
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programs that use the POSIX threading library. Regular POSIX threads, detached
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threads, mutexes, condition variables and spinlocks are supported. POSIX
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semaphores, barriers and reader-writer locks are not yet supported.
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Extensive scientific research has been carried out on the area of data-race
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detection. The two most important algorithms are known as the Eraser algorithm
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and the algorithm based on the happens-before relationship, first documented by
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Netzer. The Eraser algorithm can result in false positives, while the Netzer
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algorithm guarantees not to report false positives. The Netzer algorithm
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ignores a certain class of data races however. Both algorithms have been
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implemented in Valgrind. The helgrind tool implements the Eraser algorithm,
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and the DRD tool implements the Netzer algorithm. Although [Savage 1997]
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claims that the Netzer algorithm is harder to implement efficiently, as of
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version 3.3.0 drd runs significantly faster on several regression tests than
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helgrind.
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How to use DRD
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--------------
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To use this tool, specify --tool=drd on the Valgrind command line.
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Future DRD Versions
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-------------------
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The following may be expected in future versions of DRD:
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* More extensive documentation.
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* Drastically reduced memory consumption, such that realistic applications can
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be analyzed with DRD.
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* Faster operation.
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* Support for semaphores, barriers and reader-writer locks.
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* Support for PowerPC CPU's.
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* A lock dependency analyzer, as a help in deadlock prevention.
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* Support for more than 256 mutexes per process.
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See also
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--------
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* Robert H. B. Netzer and Barton P. Miller. What are race
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conditions? Some issues and formalizations. ACM Letters 136
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on Programming Languages and Systems, 1(1):74–88, March 1992.
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* John Ousterhout, Why Threads Are A Bad Idea (for most
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purposes), Invited Talk at the 1996 USENIX Technical Conference (January
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25, 1996). http://home.pacbell.net/ouster/threads.pdf
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* Stefan Savage, Michael Burrows, Greg Nelson, Patrick
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Sobalvarro and Thomas Anderson, Eraser: A Dynamic Data Race Detector for
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Multithreaded Programs, ACM Transactions on Computer Systems,
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15(4):391-411, November 1997.
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