Parent Thread Of Child Thread

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Parent Thread Of Child Thread

Suppose a process creates some threads say threadC and threadD.
Later on each of these threads create new child threads say threadC1, threadC2, threadC3 etc. So a tree of threads will get created.
Is there any way to find out the parent thread of one such randomly created thread?

Actually when our application starts 70 threads gets created which is as per the
requirement.
Later on as per the needs these 70 threads can create more threads.
So apart from these 70 threads a large number of other threads gets created(from
these 70 threads) and destroyed randomly.
So imagine there is a tree of threads.
There is an issue coming up in one such randomly created thread.
On debugging the code we saw that the issue will be due to a value set by its
parent thread.
So we have to find the parent thread of this erroneus thread.

We are not able to get the parent thread id of this thread?

Will anybody let us know how to find the parent of such randomly created threads
using especially windbg/visual studio?

Posted 6-Jan-11 8:52am

rupeshkp728

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#realJSOP · Answer 1 · 2011-01-06T08:58:00

Solution 1

You didn't mention what plaform/language, so I'm assuming C#.

I think the best way to do this would be to pass the creating thread in as a parameter to the ThreadStart method of the child threads. You could make it simple by deriving a new class from the existing .Net Thread class and add a new constructor that accepts a Thread as a parameter.

EDIT ============

To expand, no, there is no way to determine the parent thread of a child thread unless something like what I've mentioned has already been done.

You can put a breakpoint on the line that creates the thread, and manually make a note of the parent thread's ID, along with the new child thread's ID, but that's the best you can expect.

Posted 6-Jan-11 8:58am

#realJSOP

Updated 6-Jan-11 11:37am

v3

Comments

rupeshkp728 6-Jan-11 15:02pm

That could had been a solution.
But its the client code and so we have to debug it as of now.

#realJSOP 6-Jan-11 15:06pm

All bets are off, then. I think you're simply hosed. There are debugging techniques you can use, but even most of those require some sort of preparation in the source code (setting the Thread.Name property for instance).

rupeshkp728 6-Jan-11 15:18pm

Platform is Windows.
Lanuage is C++.
Since its the client code and so we have to debug and fix it as of now and not to make any changes in the design of client code.

fjdiewornncalwe 6-Jan-11 15:26pm

I have a very strong position that a child object should never need to be tightly coupled to the parent by requiring knowledge about them. The parent should always be the one that knows about the children and not vice-versa, but if you had to do that, regardless of language, the logic John presents here is sound.

rupeshkp728 6-Jan-11 15:58pm

Thanks John and Marcus.
But is not there any way using debuggers to find the parent like we use in process using ppid.

Sergey Alexandrovich Kryukov 6-Jan-11 20:57pm

I completely agree with Marcus.

In effect, parent-child relationship between thread should not have any use by two reasons: 1) different threads have completely unrelated stacks no matter in which stack they were created; 2) different thread can access shared resources on equal basis. In this sense, any information on where the thread was created (in which stack frame of what stack) effectively vanishes at the moment of stack creation. In other words, there are no essential differences between thread of different origin.

At the same time, for pure sport interest (there is no theoretical interest really, not mentioning practical interest) in would be funny to learn if there is a way to lean this thread "pre-history" during run-time without any static analysis.

Sergey Alexandrovich Kryukov 6-Jan-11 21:03pm

As John put it in his answer (my 5), one way to build up this relationship between thread would be creation of special thread with each thread made to carry information about it's parent thread at the moment of construction. This is absolutely correct.

Again, I see no sense in doing it.

@rupeshkp728: could you explain why are you interested in such things? Just curious.

rupeshkp728 7-Jan-11 1:51am

Thanks Sakryukov

rupeshkp728 7-Jan-11 2:01am

Hey Sakryukov the issue is coming up in the client code and so we have to debug and fix it as of now.