Hello,
from time to time we are experiencing a deadlock in the URLHandlers
Class in Apache Felix. We are using Felix as an embedded OSGi Container
and instantiate the Felix Framework via ServiceLoader and Framework
Factory ourselves. The situation is as follows: When Felix.stop and
Felix.init are called by different threads, eventually
URLHandlers.unregisterFrameworkListsForContextSearch and
URLHandlers.registerFrameworkInstance are called by the threads. There
are two locks: m_frameworks and the Class Object of URL (URL.class).
registerFrameworkInstance tries to aquire m_frameworks first and via the
constructor of URLHanders URL.class after that.
unregisterFrameworkListsForContextSearch tries to aquire URL.class first
and m_frameworks after that. This is a classic deadlock situation. The
situation arises in unittests where we frequently start and stop the
felix framework.
My questions are: Is it valid to call Felix.init after Felix.stop
without waiting if the framework actually stopped (since stop is
asyncronous)? Or do we have to wait between Felix.init and Felix.stop?
Or would you consider this a bug?
Cheers and thanks for your support,
Benjamin Rogge
P.S.: Here is a listing of the stacktraces:
Found one Java-level deadlock:
=============================
"FelixShutdown":
waiting to lock monitor 0x0000000000ff7710 (object 0x00000007ff33e7f0,
a java.util.ArrayList),
which is held by "main"
"main":
waiting to lock monitor 0x00000000022c4a08 (object 0x0000000783b06b18,
a java.lang.Class),
which is held by "FelixShutdown"
Java stack information for the threads listed above:
===================================================
"FelixShutdown":
at
org.apache.felix.framework.URLHandlers.unregisterFrameworkListsForContextSearch(URLHandlers.java:315)
- waiting to lock <0x00000007ff33e7f0> (a java.util.ArrayList)
- locked <0x00000007ff33e840> (a java.util.HashMap)
- locked <0x0000000783b06b18> (a java.lang.Class for java.net.URL)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at
org.apache.felix.framework.util.SecureAction.invoke(SecureAction.java:840)
at
org.apache.felix.framework.URLHandlers.unregisterFrameworkInstance(URLHandlers.java:635)
at
org.apache.felix.framework.URLHandlersActivator.stop(URLHandlersActivator.java:76)
at
org.apache.felix.framework.util.SecureAction.stopActivator(SecureAction.java:667)
at
org.apache.felix.framework.Felix$SystemBundleActivator.stop(Felix.java:4715)
at
org.apache.felix.framework.util.SecureAction.stopActivator(SecureAction.java:667)
at org.apache.felix.framework.Felix.stopBundle(Felix.java:2530)
at org.apache.felix.framework.Felix$2.run(Felix.java:959)
at java.lang.Thread.run(Thread.java:724)
"main":
at org.apache.felix.framework.URLHandlers.<init>(URLHandlers.java:150)
- waiting to lock <0x0000000783b06b18> (a java.lang.Class for
java.net.URL)
at
org.apache.felix.framework.URLHandlers.registerFrameworkInstance(URLHandlers.java:600)
- locked <0x00000007ff33e7f0> (a java.util.ArrayList)
at
org.apache.felix.framework.URLHandlersActivator.start(URLHandlersActivator.java:71)
at
org.apache.felix.framework.util.SecureAction.startActivator(SecureAction.java:645)
at
org.apache.felix.framework.Felix$SystemBundleActivator.start(Felix.java:4634)
at
org.apache.felix.framework.util.SecureAction.startActivator(SecureAction.java:645)
at org.apache.felix.framework.Felix.init(Felix.java:783)
// ... Application specific trace
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