WebLogic 10.3 with JDK 1.6_16 - hanging threads in Java Reflection

We are having recurring Weblogic threads hanging for 600+ seconds, or sometimes only for 30 seconds (which is just as bad) in seemingly trivial Java Reflection operations.

Thread dumps and WebLogic's own built-in alert on stuck thread all showing same native code, but no idea what could be causing it to hang for such long intervals (stuck thread below).

I noticed that message comes up, which is weird as JDK itself is jdk160_16.

This is on Solaris with Native I/O enabled, but maybe some other setting is wrong?

Various threads have different earlier code, but the stuck section is always the same:

"[STUCK] ExecuteThread: '2' for queue: 'weblogic.kernel.Default (self-tuning)'" daemon prio=3 tid=0x01c2f000 nid=0x74 runnable [0x5bcfc000]
   java.lang.Thread.State: RUNNABLE
    at java.lang.Class.getDeclaredConstructors0(Native Method)
    at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389)
    at java.lang.Class.getConstructor0(Class.java:2699)
    at java.lang.Class.newInstance0(Class.java:326)
    at java.lang.Class.newInstance(Class.java:308)
    at sun.reflect.MethodAccessorGenerator$1.run(MethodAccessorGenerator.java:381)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.reflect.MethodAccessorGenerator.generate(MethodAccessorGenerator.java:377)
    at sun.reflect.MethodAccessorGenerator.generateMethod(MethodAccessorGenerator.java:59)
    at sun.reflect.NativeMethodAccessorImp开发者_运维技巧l.invoke(NativeMethodAccessorImpl.java:28)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)