Re: [jboss-dev] Strange java.util.LinkedList.contains() NPE
Dimitris Andreadis wrote:
Digging at the logs (full trace at the bottom) I can see a strange
NPE
from java.util.LinkedList.contains(Object o), after which various
deployments get to fail:
DEBUG [org.jboss.deployment.SARDeployer] create operation failed for
package
file:/qa/services/hudson/hudson_workspace/workspace/JBoss-AS-4.2.x-TestSuite-sun15/Branch_4_2/testsuite/output/lib/receivers-arraylist-service.xml
java.lang.NullPointerException
at java.util.LinkedList.indexOf(LinkedList.java:406)
at java.util.LinkedList.contains(LinkedList.java:176)
at
org.jboss.system.ServiceController.register(ServiceController.java:828)
at
org.jboss.system.ServiceController.create(ServiceController.java:296)
at
org.jboss.system.ServiceController.create(ServiceController.java:273)
This is the ServiceController code trying to add a non-null context, so
is this really a JDK bug?
It could be a concurrency bug. The relevant code is
. . .
105 for (Entry e = header.next; e != header; e = e.next) {
106 if (o.equals(e.element))
107 return index;
108 index++;
109 }
. . .
If the list is empty at 'e = header.next' then a concurrent insert
happens before 'e != header' this could mean e is null at 'e.element'.
This would require a yield test to be placed between the loop
initializer code and the loop test which is possible depending upon the
compiler scheme for inserting yield points.
regards,
Andrew Dinn
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