(original) (raw)

(cc'ing serviceability-dev)

Thanks Steve, looks like this crept as part of some refactoring work \[1\]. Looks like PlatformLoggingMXBean has the same issue. I've created the following bug to track it:

7068328: BufferPoolMXBean and PlatformLoggingMXBean getObjectName may return null

If no one take it in the next few days then I can take it and get it push to jdk8 (listing you are contributer). The test will need a bit of clean-up, re-formatting, and throwing an exception rather than calling System.exit for example.

\-Alan

\[1\] http://hg.openjdk.java.net/jdk7/jdk7/jdk/rev/77dd50ba670b



\-------- Original Message --------
Subject: java.nio.BufferPoolMXBean getObjectName() occasionally returns null
Date: Mon, 18 Jul 2011 22:54:35 +0100
From: Steve Poole <spoole@linux.vnet.ibm.com>
To: nio-dev@openjdk.java.net 


Hi all, a small fix to a race condition that occurs under extreme and   
probably unrepresentative loading...


sun.management.ManagementFactoryHelper provides the default
implementation of java.nio.BufferPoolMXBean. The getObjectName() method
uses a volatile field to store the object name. The name is filled in
using a lazy sync method. Under high load a timing window is exposed in
which the lazy sync succeeds but a caller still recieves null.


The failing code is question is in
src/share/classes/sun/management/ManagementFactoryHelper.java


The diff and testcase are attached.


I don't know if the testcase is the right form - it creates a bunch of
threads that drive the method to expose the problem and is fairly
quick. I can show it happening on Ubuntu with JDK7 and with my local
build of JDK8.


Cheers


Steve