Mark, On 9/14/15 4:00 AM, Mark Thomas wrote: > On 13/09/2015 23:11, Caldarale, Charles R wrote: >>> From: ma...@apache.org [mailto:ma...@apache.org] >>> Subject: svn commit: r1702821 - in /tomcat/tc8.0.x/trunk: >>> java/org/apache/tomcat/util/http/HttpMessages.java >>> webapps/docs/changelog.xml >> >>> --- tomcat/tc8.0.x/trunk/java/org/apache/tomcat/util/http/HttpMessages.java >>> (original) >>> +++ tomcat/tc8.0.x/trunk/java/org/apache/tomcat/util/http/HttpMessages.java >>> Sun Sep 13 20:36:40 2015 >>> @@ -69,26 +69,34 @@ public class HttpMessages { >>> // Does HTTP requires/allow international messages or >>> // are pre-defined? The user doesn't see them most of the time >>> switch( status ) { >>> - case 200: >>> - if(st_200 == null ) { >>> - st_200 = sm.getString("sc.200"); >>> + case 200: { >>> + String s = st_200; >>> + if(s == null ) { >>> + st_200 = s = sm.getString("sc.200"); >>> } >>> - return st_200; >> >> I'm not convinced this removes the data race, since there's still no >> guarantee that the storage writes that are part of the object initialization >> inside sm.getString() will be visible to another thread before the write to >> st_200. Shipilёv's blog has some interesting studies: >> http://shipilev.net/blog/2014/safe-public-construction/ > > OK. Let me have a read of that blog. > > At the moment we have two people who claim to be expert in this area > with different opinions on whether or not the above is safe. Personally, > my money is on Chuck being right.
What's the reason for caching references to the return value of sm.getString()? Is there a significant performance advantage? -chris
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