RFR 8059533: (process) Make exiting process wait for exiting threads [win]

[Ivan Gerasimov]

On 29.10.2014 13:15, David Holmes wrote:
>
> Great improvement thanks! One further suggestion - after line 3731 add 
> a short overview eg:
>
> // Basic approach:
> //  - Each exiting thread registers its intent to exit and then does so.
> //  - A thread trying to terminate the process must wait for all
> //    threads currently exiting to complete their exit
>
>
> Typo:
> 3802           // _endthreadex() comleted.
>
Thanks! Fixed the typo and added the comment.
The updated webrev is at the same location:
http://cr.openjdk.java.net/~igerasim/8059533/1/webrev/

>
>>>
>>
>> I have a couple of thought about this:
>>
>> First, the thread that ends the process waits for all the exiting
>> threads to complete. By the time it returns from WaitForMultipleObjects,
>> those exiting threads aren't running anymore, so the race is avoided
>> (unless it's the race with scheduler).
>
> That's not quite true and the key part of my point. At some point 
> during the thread termination process the exiting thread has to signal 
> any waiting thread - and it is still running at the point. We don't 
> know whether the action that causes interference with the process 
> termination happens before or after the signalling is done.
>
I was thinking if the dedicated scheduler thread can do the signalling. 
Otherwise, some poorly behaving thread could die without updating its 
status, leaving other threads waiting for its completion forever. 
Though, I don't know how it's actually done.

I've read in several places (for example, a comment at the bottom of 
[1]), that waiting for a thread to complete with WaitForXXX() function 
ensures the exit code of that thread is set. In particular, 
GetExitCodeThread() should not return STILL_ACTIVE for that thread anymore.

This lets me hope that the code, which sets the exit code (which is 
potentially racy) has already been executed by the time WaitForXXX() 
returns.

[1] 
http://msdn.microsoft.com/en-us/library/windows/desktop/ms683190(v=vs.85).aspx

> Anyway this narrows the window even further even if it may not close 
> it completely.
>

That's my hope too :)
Otherwise, I'll be (almost) out of ideas how to work this issue around.

Sincerely yours,
Ivan