How to get the family tree of all the threads?

[Tony Guan]

Hi David,

Absolutely, I have noticed that in the experiment.

Thank you very much!

Tony

On Thu, Oct 29, 2009 at 8:54 PM, David Holmes <David.Holmes at sun.com> wrote:
> Tony,
>
> Just a note that there will be two cases where there is no currentThread:
>
> a) when the main thread is created
> b) when the main thread detaches (after executing main) and reattaches as
> the DestroyJavaVM thread.
>
> but this shouldn't affect your parent check in run()
>
> David
>
> Tony Guan wrote:
>>
>> 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
>