bug#25875: 26.0.50; Hang logging out of MS-Windows

[Richard Copley]

On 27 February 2017 at 20:58, Eli Zaretskii <eliz@gnu.org> wrote:
>> From: Richard Copley <rcopley@gmail.com>
>> Date: Mon, 27 Feb 2017 20:52:16 +0000
>> Cc: Ken Brown <kbrown@cornell.edu>, 25875@debbugs.gnu.org
>>
>> Eli, you said:
>>
>> > As I understand it, this happens because when the input thread gets
>> > the WM_ENDSESSION message, it posts it to the main thread and goes on
>> > to sleep for 1000 sec, to avoid ending the Emacs process before it
>> > finishes orderly shutdown.  But if the main thread happens to be
>> > inside redisplay, it could invoke one of the function that send
>> > messages to the input thread via SendMessage, which waits for the
>> > input thread to respond.  So we do have a kind of deadlock.
>>
>> Posting a message and then sleeping while it's processed is odd,
>> isn't it? If the input thread /sent/ its message to the main thread,
>> then while waiting for SendMessage to return, the input thread would
>> automatically continue to process sent messages
>
> No, it's the main thread that calls SendMessage, to tell the input
> thread to draw something.  And since the input thread is inside
> 'sleep', the SendMessage call never returns, and the main thread never
> gets around to checking its input queue, where there's an event bound
> to kill-emacs, waiting to be processed.

Please Eli, read what I said again. It might not be right, but you
misunderstood it.
I know the input thread isn't calling SendMessage. It's callling PostMessage and
then sleep. I'm suggesting that the input thread should call SendMessage.