IV25687: DEADLOCK BETWEEN APPCLASSLOADER AND CUSTOM CLASSLOADER AFTER APPLYING APAR IZ96932

APAR status

• Closed as program error.

Error description

• Error Message: Customer observed the deadlock after upgrading
  from 50SR12 to 50Sr13:-
  1LKDEADLOCK    Deadlock detected !!!
  NULL           ---------------------
  NULL
  2LKDEADLOCKTHR  Thread "WebContainer : 5" (0x3A1BA300)
  3LKDEADLOCKWTR    is waiting for:
  4LKDEADLOCKMON      sys_mon_t:0x3410FFE0 infl_mon_t: 0x34110008:
  4LKDEADLOCKOBJ
  sun/misc/Launcher$AppClassLoader@7002A0B0/7002A0BC:
  3LKDEADLOCKOWN    which is owned by:
  2LKDEADLOCKTHR  Thread "WebContainer : 6" (0x3A1BA700)
  3LKDEADLOCKWTR    which is waiting for:
  4LKDEADLOCKMON      sys_mon_t:0x35F1DB80 infl_mon_t: 0x35F1DBA8:
  4LKDEADLOCKOBJ
  org/eclipse/core/launcher/Main$StartupClassLoader@705D49C0/705D4
  9CC:
  3LKDEADLOCKOWN    which is owned by:
  2LKDEADLOCKTHR  Thread "WebContainer : 5" (0x3A1BA300)
  NULL
  .
  Stack Trace: Stacks of the threads involved in deadlock:-
  3XMTHREADINFO      "WebContainer : 5" (TID:0x3A1BA300,
  sys_thread_t:0x39B179D4, state:B, native ID:0x0114701B) prio=5
   at
  java/lang/ClassLoader.loadClass(ClassLoader.java:642(Compiled
  Code))
   at java/lang/ClassLoader.loadClass(ClassLoader.java(Compiled
  Code))
   at
  org/eclipse/osgi/framework/internal/core/BundleLoader.findClass(
  BundleLoader.java:352(Compiled Code))
   at
  org/eclipse/osgi/framework/internal/core/BundleLoader.findClass(
  BundleLoader.java:347(Compiled Code))
   at
  org/eclipse/osgi/internal/baseadaptor/DefaultClassLoader.loadCla
  ss(DefaultClassLoader.java:79(Compiled Code))
   at
  java/lang/ClassLoader.loadClass(ClassLoader.java:642(Compiled
  Code))
   at
  com/ibm/ws/bootstrap/ExtClassLoader.loadClass(ExtClassLoader.jav
  a:87(Compiled Code))
   at
  java/lang/ClassLoader.loadClass(ClassLoader.java:616(Compiled
  Code))
   at
  com/ibm/ws/classloader/ProtectionClassLoader.loadClass(Protectio
  nClassLoader.java:58(Compiled Code))
   at
  com/ibm/ws/classloader/ProtectionClassLoader.loadClass(Protectio
  nClassLoader.java:54(Compiled Code))
   at
  com/ibm/ws/classloader/CompoundClassLoader.loadClass(CompoundCla
  ssLoader.java:399(Compiled Code))
   at
  java/lang/ClassLoader.loadClass(ClassLoader.java:616(Compiled
  Code))
   at
  com/ibm/ws/classloader/CompoundClassLoader.loadClass(CompoundCla
  ssLoader.java:399(Compiled Code))
   at
  java/lang/ClassLoader.loadClass(ClassLoader.java:616(Compiled
  Code))
   at
  org/apache/xerces/parsers/ObjectFactory.findProviderClass(Byteco
  de PC:55)
   at org/apache/xerces/parsers/ObjectFactory.newInstance(Bytecode
  PC:3)
  3XMTHREADINFO      "WebContainer : 6" (TID:0x3A1BA700,
  sys_thread_t:0x39B17C70, state:B, native ID:0x00E8F00D) prio=5
   at
  java/lang/ClassLoader.loadClass(ClassLoader.java:616(Compiled
  Code))
   at java/lang/Class.forNameImpl(Native Method)
   at java/lang/Class.forName(Class.java:130(Compiled Code))
   at
  org/eclipse/osgi/framework/util/SecureAction.forName(SecureActio
  n.java:309(Compiled Code))
   at
  org/eclipse/osgi/framework/internal/protocol/StreamHandlerFactor
  y.getBuiltIn(StreamHandlerFactory.java:58(Compiled Code))
   at
  org/eclipse/osgi/framework/internal/protocol/StreamHandlerFactor
  y.createURLStreamHandler(StreamHandlerFactory.java:86)
   at java/net/URL.getURLStreamHandler(URL.java:1142(Compiled
  Code))
   at java/net/URL.<init>(URL.java:607(Compiled Code))
   at java/net/URL.<init>(URL.java:499(Compiled Code))
   at
  sun/misc/URLClassPath$FileLoader.getResource(URLClassPath.java:1
  158(Compiled Code))
   at
  sun/misc/URLClassPath$FileLoader.findResource(URLClassPath.java:
  1148(Compiled Code))
   at
  sun/misc/URLClassPath.findResource(URLClassPath.java:301(Compile
  d Code))
   at
  java/net/URLClassLoader$3.run(URLClassLoader.java:806(Compiled
  Code))
   at
  java/security/AccessController.doPrivileged(AccessController.jav
  a:214)
   at
  java/net/URLClassLoader.findResource(URLClassLoader.java:803(Com
  piled Code))
   at
  java/lang/ClassLoader.getResource(ClassLoader.java:431(Compiled
  Code))
   at
  java/lang/ClassLoader.getResource(ClassLoader.java:426(Compiled
  Code))
  .
  N/A
  

Local fix

• N/A
  

Problem summary

• The OSGi framework of WAS runs on does its own protocol
  handling.  When a resource is loaded, it tries to load the
  protocol handler using Class.forName.  The loader which use to
  load the OSGi classes is a child of Launcher$AppClassLoader, so
  when it tries to load the handler, it already has the lock on
  AppClassLoader (due to the URLClassLoader.findResource API
  synchronization) but then tries to load from a child loader.  In
  parallel if some other thread is going down a standard loadClass
  path it already has that child classloader lock and will require
  the AppClassLoader and hence the deadlock.
  

Problem conclusion

• This defect will be fixed in:
  5.0.0 SR14
  .
  The JVM has been updated to handle the deadlock scenario when
  custom classloaders loads the classes in above fashion.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  JAVA 5 CLASS LI

• Fixed component ID

  620500130

Applicable component levels

• R500 PSY

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