JVMDI Launching and Thread Suspension

Question

Hi,
I am using JVMDI to debug a java application. I launch the application and debugger with the following command line.
java -Xdebug -Xnoagent -XrunTest:ADA <applicationName>
When I try and suspend the application after a method entry event, everything (including my JVMDI debugger) is suspended. This is not what I had thought would happen. I only want the application thread to suspend so that I can access the stack frames. Is there a problem with the way I am loading the application and debugger � or am I suspending that application incorrectly (see below).
err = jvmdi->GetMethodLocation((*event).u.frame.clazz,
(*event).u.frame.method,
&startLocationPtr, &endLocationPtr);
err = jvmdi->GetMethodName((*event).u.frame.clazz,
(*event).u.frame.method,
&namePtr, &signaturePtr);
err = jvmdi->GetSourceFileName((*event).u.frame.clazz,&SourceNamePtr);
/* is this the application class or a system class */
if ((strncmp(prefix,SourceNamePtr,prefixLength) == 0))
err = jvmdi->SuspendThread((*event).u.frame.thread);
Any help would be greatly appreciated.
Chief

Answer 1

Are you running your JVMDI code on the same thread as the
application? If so, then SuspendThread will indeed suspend
everything, and your code will not be able to resume itself.
Is (*event).u.frame.thread the same as `this` thread in your code?
Then you are suspending yourself. You will need to take pains
to run your code on a Debug thread. See "RunDebugThread" at this URL:
http://java.sun.com/j2se/1.4.1/docs/guide/jpda/jvmdi-spec.html#RunDebugThread
It would be less intrusive on the debugee if you wrote
an out-of-process debugger that attached to the debugee
using the Java Debug Interface (JDI). For more information,
refer to the Architecture Overview document:
http://java.sun.com/j2se/1.4.1/docs/guide/jpda/architecture.html
JDI has an added advantage: it is a Java Language API, which
means you can write your debugger in the Java Language. There
is a reference debugger (jdb) with source available for you to
study. Unpack $JAVA_HOME/demo/jpda/examples.jar, and
then look at
Trace.java and TTY.java (and their related support classes).