Getting a thread dump from a frozen Java app without using JStack

Question

When I am trying to use JStack to get the thread dump of my frozen application, one of the threads gives me this result:

Thread 27560: (state = IN_NATIVE)
 - org.eclipse.swt.internal.gtk.OS._gtk_adjustment_changed(int) @bci=0 (Compiled frame; information may be imprecise)
Error occurred during stack walking:
java.lang.NullPointerException
    at sun.jvm.hotspot.runtime.Frame.addressOfStackSlot(Frame.java:224)
    at sun.jvm.hotspot.runtime.x86.X86Frame.senderForCompiledFrame(X86Frame.java:342)
    at sun.jvm.hotspot.runtime.x86.X86Frame.sender(X86Frame.java:283)
    at sun.jvm.hotspot.runtime.Frame.sender(Frame.java:194)
    at sun.jvm.hotspot.runtime.Frame.realSender(Frame.java:199)
    at sun.jvm.hotspot.runtime.VFrame.sender(VFrame.java:119)
    at sun.jvm.hotspot.runtime.CompiledVFrame.sender(CompiledVFrame.java:178)
    at sun.jvm.hotspot.runtime.VFrame.javaSender(VFrame.java:146)
    at sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:76)
    at sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:45)
    at sun.jvm.hotspot.tools.JStack.run(JStack.java:60)
    at sun.jvm.hotspot.tools.Tool.start(Tool.java:221)
    at sun.jvm.hotspot.tools.JStack.main(JStack.java:86)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at sun.tools.jstack.JStack.runJStackTool(JStack.java:118)
    at sun.tools.jstack.JStack.main(JStack.java:84)

Of course, it is the one I am most interested in :(

Ctrl+Break doesn't work either. Are there other ways to get a thread dump? I am using Linux and Sun VM 1.6.0_20.

Answer 1

On Linux you might have to use Ctrl+\ in the terminal to generate a thread dump as you do on UNIX systems.

Answer 2

You could try VisualVM, a free tool that is bundled with Java 6. I believe it's available for Linux as well as other operating systems.

This allows you to remotely connect to running Java processes, do thread / heap / application dumps, as well as profiling and other useful tools.

See https://visualvm.dev.java.net/ for more information.