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Date: Thu, 6 Aug 2020 16:26:14 +0200
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: Race condition hangs on multiple mintty/tcsh? Brad Wetmore
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On Aug  6 15:31, Thomas Wolff wrote:
> Am 06.08.2020 um 13:46 schrieb Thomas Wolff:
> > Am 06.08.2020 um 01:23 schrieb Kevin Schnitzius via Cygwin:
> > > On Wednesday, August 5, 2020, 06:56:48 PM EDT, Thomas Wolff
> > > <towo@towo.net> wrote:
> > > > Am 04.08.2020 um 12:02 schrieb Thomas Wolff:
> > > > > Am 04.08.2020 um 00:13 schrieb Brad Wetmore via Cygwin:
> > > > > > Hi,
> > > > > > 
> > > > > > I generally kick off multiple (10) mintty sessions, and place them
> > > > > > around the screen.
> > > > > > 
> > > > > > C:/cygwin64/bin/mintty.exe -i /Cygwin-Terminal.ico \
> > > > > --position @3 --position 120,0 --size 80x71 /bin/tcsh &
> > > > > > C:/cygwin64/bin/mintty.exe -i /Cygwin-Terminal.ico \
> > > > > > --position @3 --position 715,0 --size 80x45 /bin/tcsh &
> > > > > > C:/cygwin64/bin/mintty.exe -i /Cygwin-Terminal.ico \
> > > > > > --position @3 --position 715,660 --size 80x24 /bin/tcsh &
> > > > > > 
> > > > > > Within the last 6 months or so, about 2-3 of them would hang and
> > > > > > either mintty/tcsh would not start. I put a "sleep 1" in between each
> > > > > > invocation and that seemed to take care of it.
> > > > > > 
> > > > > > With the latest cygwin update, about 8 of them just hang even with
> > > > > > the sleep 1. I put in a "sleep 2", and now everything is coming up
> > > > > > again.
> > > > > > 
> > > > > > Not sure if this is a mintty or tcsh issue, but just wondering if
> > > > > > others are seeing this before I start trying to debug this.
> > > > > I can reproduce such behaviour with /bin/bash (easy cross-check), and
> > > > > in fact the shell is running in that case (easy test via `echo >
> > > > > .log`), so I have a vague and unpleasant suspicion it might in fact be
> > > > > related to mintty although I have no idea how that would happen. To be
> > > > > analysed.
> > > > When in this state, on the pty from which mintty receives child process
> > > > output, select() does not report a ready for reading condition;
> > > > could it
> > > > be related to the recent poll/select patch? I could not reproduce it in
> > > > cygwin 3.0.7.
> > > for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ; do
> > > mintty  -i /Cygwin-Terminal.ico  --position @3 --position 120,$i
> > > --size 80x24 /bin/bash & done
> > > 
> > > This does not fail for me.  Nor does it fail from cmd or powershell
> > > using a script.
> > > 
> > > I tried 3.1.4 and 3.1.6 on Windows 10.  I tried up to 100 instances
> > > of of mintty...
> > Thanks for testing. It is in fact hard to reproduce, maybe also
> > depending on system load (speculating).
> > I could reproduce one case of one of three terminals being unresponsive
> > also with xterm.
> And it also happens if I drop select() from mintty (and use just
> non-blocking read()).
> > Does anybody familiar with pty/select or recent changes have any idea?
> ?

Something with the pseudo console?  Can you test w/o pseudo console code,
just to check?

Other than that we probably need some bisecting to find the cause.


Corinna

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Corinna Vinschen
Cygwin Maintainer
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