Re: PATCH: pg_restore parallel-execution-deadlock issue

On Fri, May 27, 2016 at 4:07 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Fri, May 27, 2016 at 3:05 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>
>> Michael Paquier <michael(dot)paquier(at)gmail(dot)com> writes:
>> > ea274b2 has changed the way disconnection is done is is now closing
>> > both the read and write pipes. So you may want to retry if things get
>> > better with the next round of minor releases.
>>
>> Hadn't paid attention to this thread before ...
>>
>> 1. Armin proposes using "shutdown(pipeWrite, SD_BOTH)" where the code
>> committed this morning (df8d2d8c4) has "closesocket(pipeWrite)".
>> I'd prefer to leave it that way since it's the same as for the Unix case,
>> and Kyotaro-san says it works for him. Is there a reason we'd need
>> shutdown() instead?

Hm, OK.

>> 2. Armin proposes that WaitForTerminatingWorkers needs to do CloseHandle()
>> on the various thread handles. That sounds plausible but I don't know
>> enough Windows programming to know if it really matters.
>>
>> 3. Should we replace ExitThread() with _endthreadex()? Again, it
>> seems plausible but I'm not the person to ask.
>>
>
> I think point (2) and (3) are related because using _endthreadex won't close
> the thread handle explicitly [1].

Yep.

> [1] - https://msdn.microsoft.com/en-us/library/kdzttdcb.aspx
> Refer line "_endthread automatically closes the thread handle, whereas
> _endthreadex does not."

And the rest of the sentence:
Therefore, when you use _beginthread and _endthread, do not explicitly
close the thread handle by calling the Win32 CloseHandle API. This
behavior differs from the Win32 ExitThread API.

Personally I understand that as well as for the first part: when using
_beginthreadex and _endthreadex, be sure to call CloseHandle() to
explicitely close the thread handle.

And based on the second part if we use ExitThread after beginning a
thread with _beginthreadex we would get unreliable behavior. I guess
you don't need a patch? Because by looking again at this thread and
the windows docs what we have now is unpredictable.
--
Michael