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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