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From "Weldon Washburn" <weldon...@gmail.com>
Subject [drlvm][reliability tests] Harmony-2986, Dekker's algorithm -- is this a valid test for modern SMP hardware?
Date Wed, 21 Feb 2007 06:03:13 GMT
It seems Dekker's algorithm is not expected to work on SPARC or IA32 SMP
boxes unless memory fences are used.  DekkerTest.java in Harmony-2986 does
not contain memory fences.  The volatile keyword guarantees the compiler
will write a given variable to memory.  However, the HW may actually have a
write buffer and allow reads to pass writes.  As far as I know, the Java
language does not provide a means to invoke a memory fence.  Thus there is
no way to fix up DekkerTest.java.  I may be misunderstanding something
here.  Does anyone have comment?

An excellent description of the issues involved is in a David Dice
presentation at:

http://blogs.sun.com/dave/resource/synchronization-public2.pdf

-- 
Weldon Washburn
Intel Enterprise Solutions Software Division

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