How to get the family tree of all the threads?

[Tony Guan]

Hi David &  Alan & Christian,

Thank you all for the prompt reply! I am currently using such an
approach as the following, could you please take a look to see if
something might be wrong?

1) added a Thread* field for the JavaThread:
  Thread*  _parent; //to memorize the thread which creates this thread.
2) get the current thread running when a new JavaThread is created,
this current thread should be the parent of the to-be created thread,
in JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz)
:
    _parent=Thread::current(); //tony: we added it for convenience.
3)verify the _parent field in the run() method of the newly created
thread, by this time, the current thread should be the child thread
created.
   int ostid_parent=_parent->osthread()->thread_id();

Then if the child thread is ever running, I can get its parent thread.

Thanks a lot!

Tony

On Thu, Oct 29, 2009 at 6:39 AM, David Holmes <David.Holmes at sun.com> wrote:
> Hi Tony,
>
>> I am working on a project where I need to identify the relations
>> between parent threads and children threads. Especially, I want to do
>> it inside the JVM, not in a java program.
>
> As others have said you need to do this yourself by monitoring thread
> construction and/or starting.
>
> In Java there is no parent/child relationship between threads - all threads
> are considered equal siblings. This is in contrast to other systems where
> "child" threads are an explicit notion where exceptions in a child can be
> caught in a parent; where joining a parent joins all children etc. But
> that's not Java.
>
> Cheers,
> David Holmes
>
>> Looking at the code of hotspot, I can only find the thread list inside
>> the Thread class, but it's not enough for my purpose.
>>
>> Is there some way that I can draw out a family tree of the threads
>> within the hotspot? I know that from within a java program, we can
>> draw a tree of all the ThreadGroups, but it again is not what I want.
>>
>> Or could you tell me how I could identify when a thread is created,
>> and who is the parental thread that creates it?
>>
>> Thanks a lot!
>>
>> Tony Guan
>