Deadlock with class loading and URLHandlers
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Key: FELIX-748
URL: https://issues.apache.org/jira/browse/FELIX-748
Project: Felix
Issue Type: Bug
Components: Framework
Affects Versions: felix-1.0.4
Reporter: Felix Meschberger
Attachments: FELIX-748-deadlock.txt
We have a tricky dead lock issue involving Java ClassLoaders and the Felix
framework URLHandlers class. We have two web apps: An Apache Sling web app
using Felix as its framework and a second Web App providing a JCR repository.
While starting up, someone is accessing the JCR repository web app which causes
a JSP compilation. This involves class loading and calls into the Felix
URLHandlers to create some URL.
The deadlock description is:
Found one Java-level deadlock:
=============================
"SimpleQuartzScheduler_QuartzSchedulerThread":
waiting to lock monitor 0x0aaa6634 (object 0x03256ac0, a
java.net.URLClassLoader),
which is held by "SCR Component Actor"
"SCR Component Actor":
waiting to lock monitor 0x0aaa65cc (object 0x02ebba58, a
java.net.URLClassLoader),
which is held by "127.0.0.1 [1222693412656] GET /crx/browser/index.jsp
HTTP/1.1"
"127.0.0.1 [1222693412656] GET /crx/browser/index.jsp HTTP/1.1":
waiting to lock monitor 0x0aaa6634 (object 0x03256ac0, a
java.net.URLClassLoader),
which is held by "SCR Component Actor"
Looking at the code, it seems, that the URLHandlers.createURLStreamHandler
class is using a synchronized blog which looks too big. In addition it uses the
SecureAction.forName method, which in turn uses Class.forName, which has its
issues, too.
So maybe the URLHandlers.createURLStreamHandler method should employ a
different synchronization mechanism so as to avoid deadlocks through
classloaders.
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