Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!aioe.org!eternal-september.org!feeder.eternal-september.org!mx04.eternal-september.org!.POSTED!not-for-mail
From: markspace <-@.>
Newsgroups: comp.lang.java.programmer
Subject: Re: reading the JLS (17.4.5)
Date: Tue, 20 Dec 2011 10:50:53 -0800
Organization: A noiseless patient Spider
Lines: 25
Message-ID: <jcqlef$5rp$1@dont-email.me>
References: <slrnjerm1c.fvg.avl@gamma.logic.tuwien.ac.at> <jckv1o$v1v$1@dont-email.me> <slrnjf1iug.fvg.avl@gamma.logic.tuwien.ac.at>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Date: Tue, 20 Dec 2011 18:50:55 +0000 (UTC)
Injection-Info: mx04.eternal-september.org; posting-host="XjIWM99mD7Ijfdu600oVPA"; logging-data="6009"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX18BSUDFXBi39ojnDfHFss4QTxri6hYUTDA="
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:8.0) Gecko/20111105 Thunderbird/8.0
In-Reply-To: <slrnjf1iug.fvg.avl@gamma.logic.tuwien.ac.at>
Cancel-Lock: sha1:bnv8S/LvHhl5Qgh0uCMxxsgQa7E=
Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.programmer:10909

On 12/20/2011 9:54 AM, Andreas Leitgeb wrote:

> I guess, I got confused about the implications of the property,
> based on that it was defined as a property of a set of actions,
> rather than as a property of a conforming JVM-implementation.


I'm not sure why those exceptions are there, but that little paragraph 
is a pretty common sense, cya exception.  You wont see a write if it 
hasn't happened yet, and you wont see the effect of a write if someone 
else wrote something there subsequently, before your read.

"Conforming JVM" is a pretty good guess, I think, but personally I 
couldn't say.

Patricia had some thoughts on reordering by hardware, but that involved 
synchronization and memory barriers, and I don't recall seeing those 
discussed in the small JLS section in question.  I think this JLS 
section applies more generally than a read or write getting moved out of 
a synchronization block.  I think it applies absolutely everywhere.