[PATCH draft 0/6] Remove the fhandler_base_overlapped class

[Ken Brown]

On 6/11/2019 12:42 PM, Michael Haubenwallner wrote:
> 
> 
> On 6/11/19 10:48 AM, Corinna Vinschen wrote:
>> Hi Ken,
>>
>> On Jun  8 12:20, Ken Brown wrote:
>>> On 6/7/2019 5:43 PM, Ken Brown wrote:
>>>> On 6/7/2019 3:13 PM, Ken Brown wrote:
>>>>> On 6/7/2019 2:31 PM, Achim Gratz wrote:
>>>>>> Ken Brown writes:
>>>>>>> I think I've found the problem.  I was mishandling signals that arrived during a
>>>>>>> read.  But after I fix that, there's still one nagging issue involving timerfd
>>>>>>> code.  I'll write to the main list with details.  I *think* it's a timerfd bug,
>>>>>>> but it's puzzling that I only see it when testing my new pipe implementation.
>>>>>>
>>>>>> Anything triggering a race or deadlock will depend on so many other
>>>>>> things that it really is no surprise to see seemingly unrelated changes
>>>>>> making the bug appear or disappear.  There are certainly races left in
>>>>>> Cygwin, I see them from time to time in various Perl modules, just never
>>>>>> reproducible enough to give anyone an idea of where to look.
>>>>>
>>>>> That makes sense.
>>>>>
>>>>> In the meantime, I've already discovered another problem, within an hour of
>>>>> posting my claim that everything was working fine: If I start emacs-X11 with
>>>>> cygserver running, I can't fork any subprocesses within emacs.  I get
>>>>>
>>>>> 0 [main] emacs 2689 dofork: child 2693 - died waiting for dll loading, errno 11
>>>>>
>>>>> Back to the drawing board....  I've never looked at the cygserver code, but
>>>>> maybe it will turn out to be something easy.
>>>>
>>>> Good news (for me): This isn't related to my pipe code.  The same problem occurs
>>>> if I build the master branch.  I'll bisect when I get a chance (probably
>>>> tomorrow).  In the meantime, all I can say is that strace shows a
>>>> STATUS_ACCESS_VIOLATION at shm.cc:125.
>>>
>>> A bisection shows that the problem starts with the following commit:
>>
>> Thanks for bisecting!
>>
>>> commit f03ea8e1c57bd5cea83f6cd47fa02870bdfeb1c5
>>> Author: Michael Haubenwallner <michael.haubenwallner@ssi-schaefer.com>
>>> Date:   Thu May 2 12:12:44 2019 +0200
>>>
>>>       Cygwin: fork: Remember child not before success.
>>>
>>>       Do not remember the child before it was successfully initialized, or we
>>>       would need more sophisticated cleanup on child initialization failure,
>>>       like cleaning up the process table and suppressing SIGCHILD delivery
>>>       with multiple threads ("waitproc") involved.  Compared to that, the
>>>       potential slowdown due to an extra yield () call should be negligible.
>>
>> Please revert the patch for the time being.  Michael, this needs some
>> more work, apparently.
> 
> Because of https://cygwin.com/ml/cygwin/2019-06/msg00110.html:
> Is there still some problem related to that commit I need to figure out?

Yes.  That was an unrelated issue AFAIK.

Ken