Re: JavaMemoryModel: Programmer Oriented FAQ

From: Sylvia Else (sylviae@optushome.com.au)
Date: Wed Feb 11 2004 - 19:16:32 EST


Hi,

In the FAQ you appear to be suggesting that there is no longer any point in
trying to implement the double checked lock parradigm, because the cost of
using a volatile approaches that of locking under JSR133.

On the 30th of October, on this list, Hans Boehm replied to a question of
mine on this subject, under the topic "Re: JavaMemoryModel: JMM and caches."

The answer I got there seemed to indicate that, at least on some
architectures, we can still expect locking to have a significant cost
compared with the use of volatile. This shouldn't be surprising, because
locking provides an additional guarantee of atomicity w.r.t to other
accesses of the same memory location that a simple volatile read or write
does not.

Sylvia.

At 04:58 PM 11/02/2004 -0500, you wrote:
>Hi folks,
>
>Brian Goetz and I have put together an introduction to memory model issues
>which may be more accessible to the average multithreaded programmer. It
>is probably a useful document to publicize to those who may ask you about
>these issues.
>
>Also, we'd like to hear your feedback, if you have any.
>
>It's available at:
>
>http://www.cs.umd.edu/users/jmanson/java/jsr-133-faq.html
>
> Jeremy
>-------------------------------
>JavaMemoryModel mailing list - http://www.cs.umd.edu/~pugh/java/memoryModel

-------------------------------
JavaMemoryModel mailing list - http://www.cs.umd.edu/~pugh/java/memoryModel



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