JDK-7073491 : -Dsun.net.maxDatagramSockets=1 does not work correctly with system.gc()
  • Type: Bug
  • Component: core-libs
  • Sub-Component: java.net
  • Affected Version: 7
  • Priority: P3
  • Status: Closed
  • Resolution: Fixed
  • OS: windows_xp
  • CPU: x86
  • Submitted: 2011-08-01
  • Updated: 2013-09-12
  • Resolved: 2011-10-04
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JDK 7 JDK 8
7u2Fixed 8 b08Fixed
Related Reports
Relates :  
JDK-7091369 - DatagramSocket/Limit.java failing on 8 and 7u2
Relates :  
JDK-7098719 - -Dsun.net.maxDatagramSockets and Socket constructor does not work correctly with System.gc()
Description
When System.gc() is launched in a test program, the test program creates Sockets
more than the limit specified in -Dsun.net.maxDatagramSockets.

CONFIGURATION:
OS :WinXP(SP3, Japanese, x86)
JDK : JDK7GA
java version "1.7.0"
Java(TM) SE Runtime Environment (build 1.7.0-b147)
Java HotSpot(TM) Client VM (build 21.0-b17, mixed mode)

REPRODUCE:
1. Compile the attached Limit.java 
   (javac -Xlint:deprecation Limit.java)
2. jar -cvf J800275.jar *.class
3. del *.class
4. java -Djava.security.policy=Limit.policy -Dsun.net.maxDatagramSockets=1 -cp J800275.jar Limit

The message shows up,

Exception in thread "main" java.lang.RuntimeException: Test failed (a): limit was set to 1
        at Limit.main(Limit.java:33)

Please see comment section for a little bit more detail.
Comments
Changeset: http://hg.openjdk.java.net/jdk8/tl/jdk/rev/9281d65f911a author michaelm Thu Sep 15 13:50:30 2011 +0100 (24 months ago) changeset 4560 9281d65f911a parent 4519 43880d125b79 child 4561 34fc7bbbb465 http://hg.openjdk.java.net/jdk8/tl/jdk/rev/9281d65f911a
05-09-2013
EVALUATION The problem is in AbstractPlainDatagramSocket.create(). If ResourceManager.beforeUdpCreate() throws an exception then fd is left set in the impl object. And if the finalizer for this object runs then it will attempt to close the object and decrement the counter, thus double counting the close. It only happens via the finalizer because the impl is not returned to the application because the original exception is thrown from a DatagramSocket constructor.
04-08-2011