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

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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 number

    IV25687

  • Reported component name

    JAVA 5 CLASS LI

  • Reported component ID

    620500130

  • Reported release

    500

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-08-04

  • Closed date

    2012-08-16

  • Last modified date

    2012-09-05

  • 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

       UP



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Document information


More support for:

Runtimes for Java Technology
Java Class Libraries

Software version:

5.0

Reference #:

IV25687

Modified date:

2012-09-05

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