Checking if a thread is working

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3.67/5 (3 votes)

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I am learning threading and I was wondering if there was a way to check if a thread was working or not, something like this.

VB

If thread1.working then
    thread2.join()
    thread2 = new thread(address of somemethod)
    thread2.start()
else
    thread1.join()
    thread1 = new thread(address of somemethod)
    thread1.start()
end if

I am not looking for code, just resources on how this would work.

Posted 17-Dec-12 2:57am

Daniel Verbatim Hallam

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Sergey Alexandrovich Kryukov 17-Dec-12 10:04am

Why, exactly?
—SA

3 solutions

Solution 1

That depends on what you mean by "working". You can only get the status of a thread (IsRunning), but you cannot get the status of the code it's executing.

The only way to do that would be to rewrite the code your background thread is running to provide some sort of "heartbeat" or some other status variable or events that your parent code can check or subscribe to.

Posted 17-Dec-12 3:17am

Dave Kreskowiak

Comments

Daniel Verbatim Hallam 17-Dec-12 9:22am

Would I be right to assume that once the method the thread is executing has completed the thread would no longer be running?

Dave Kreskowiak 17-Dec-12 9:33am

Once the the code is done the thread dies. It will no longer be running.

Solution 3

CPallini answered you, but the polling of the thread for status is a sign of really wrong design.

In some situations, you need a blocking call System.Threading.Thread.Join. The calling thread will be put in wait state, sleeping without wasting any CPU cycles, until awakened by completion. Please see:
http://msdn.microsoft.com/en-us/library/system.threading.thread.join.aspx[^].

I see you already trying "if (working) thread.Join()", but this is pointless, really. Explain what you are trying to achieve, the purpose of it.

In other cases, it's the best for a thread to notify other threads on completion. How? It depends. Please see my comments to Solution 2.

—SA

Posted 17-Dec-12 4:00am

Sergey Alexandrovich Kryukov

Updated 17-Dec-12 4:04am

v3

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CPallini · Accepted Answer · 2012-12-17T03:20:00

Solution 2

Do you mean Managed Thread States [^]?

Posted 17-Dec-12 3:20am

CPallini

Comments

Daniel Verbatim Hallam 17-Dec-12 9:24am

Thats a useful link too, I was looking for something like that, thank you.

CPallini 17-Dec-12 9:33am

you are welcome.

Sergey Alexandrovich Kryukov 17-Dec-12 9:57am

This is useful, good to know, my 5, but...

It's much better not to poll the thread at all and not depend on return. It's much better to design a thread to notify require set on completion; another approach is to wait for thread completion by Join, which is a blocking code, without wasteful polling; is some situations, this is exactly what should be done.

This way, the real solution of the problem depends on the purpose OP did not share with us.
—SA

Espen Harlinn 17-Dec-12 12:33pm

5'ed!