Com.sun.jdi.ThreadReference.frames() unexpectedly raises an exception

Question

Hi,
I'm using JDI for monitoring and manipulating another jvm running on the same machine.
For retrieving the stackframes of a thread, I call thread.frames(). This call is said to raise a IncompatibleThreadStateException if the corresponding thread on the debugged jvm is not suspended. However, I sometimes encounter situations where this exception is raised even when the thread is suspended ! Furthermore, in this case, the duration of the call thread.frames() is between 1.8 and 2 seconds (instead of a few milliseconds in normal cases().
// now, the jvm is stopped at a breakpoint
ThreadReference thread = .....;
if (thread.isSuspended()) { // will obviously be true
List frames = thread.frames();
// the frames() call may raise an exception and takes up to 2 sec.
Is this a known bug ? Is the API's doc incomplete ? Can someone explain me what's happends, or comment about this strange behaviour ?
Thanks in advance,
Jacques-Olivier
[email protected]

Answer 1

Can't help, but this happens to me too. Here is a code snippet:
tr.suspend();
try
System.out.println("Suspended: "+tr.isSuspended());
List lFrames=tr.frames();
finally
tr.resume();
This code snippet always prints 'suspended: true' and always throws the exception on the tr.frames() call, in my code. (running on 1.4.1 FCS, connected using a com.sun.jdi.CommandLineLaunch)
(Incidentally, my code actually intends to suspend the entire VM, not individual threads. But I threw in the suspend of an individual thread in addition, just in case.)
--sam