java.nio.BufferPoolMXBean getObjectName() occasionally returns null (original) (raw)

Steve Poole spoole at linux.vnet.ibm.com
Mon Jul 18 22:51:27 PDT 2011

On 19/07/11 05:09, Alan Bateman wrote:

(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. Thanks Alan. I wasn't sure of the testcase form to use for a multithreaded problem - I will be curious to see how it ends up. -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 at linux.vnet.ibm.com> To: nio-dev at 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

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