Re: -nolisten tcp -multiwindow combination crashes in XWin startup

[Dave <temp131@ymail.com>]

Jon:  Thanks for the pointers to the fork() problem faqs.  That and a bit of googling led me to give rebaseall a try, and
that appears to have cured my issue.  (For others, instructions can be found at
http://www.heikkitoivonen.net/blog/2008/11/26/cygwin-upgrades-and-rebaseall/ .)

Suggestion, perhaps more to the main cygwin team:  Since this issue is cygwin specific and is a bit obscure (I've
been using cygwin for a good many years, but this is the first time I've recognized I had issues from this), it'd be nice
if users didn't have to learn about this the hard way.  Could running rebaseall perhaps be automated as part of setup.com?


----- Original Message -----
From: Jon TURNEY

Sent: Tuesday, November 1, 2011 6:52 AM
Subject: Re: -nolisten tcp -multiwindow combination crashes in XWin startup

On 31/10/2011 19:22, Dave wrote:
> Sadly this one wants to play a little hard to get...
> 
> I have tried this on two somewhat similar machines - 5 years difference in hardware, but both XP Pro up-to-date on Microsoft Update, and both running the cygwin versions present on mirror.mcs.anl.gov as of this weekend - both were upgraded, then after both were, I checked that there were no further upgrades posted in between.  The two differ regarding which packages are present, but for those present, they'd seem to be at the same versions.
> 
> One shows this problem quite consistently, the other doesn't show it at all.  It's the newer one, which has a good amount of memory to spare and is usually the more reliable these days, that is showing the problem.
> 
> I can recreate the problem at will on the one that shows it by starting XWin at the command line directly, under xinit, or under startxwin.  But if I try to start XWin under gdb, I don't see the problem; see below.  (The page you pointed me to suggests attaching gdb after startup, but that doesn't seem reasonable in this case.)
> 
> I notice in the output from starting XWin at the command line there's the line
>        3 [main] XWin 4520 fork: child 5408 - died waiting for dll loading, errno 11
> I didn't see this output or captured in /var/log/xwin/XWin.0.log when I ran via xinit or startxwin.  I don't know if that line got generated but lost in output redirections, or if this way of starting X is maybe seeing yet a different problem.  This line seems similar to that reported by Denis Beauchemin, Wed, 19 Oct 2011 14:17:54 +0000.

Yes, this line is output directly by the cygwin DLL, so you won't see it in XWin.0.log

This output is typical of some other software causing cygwin problems with fork emulation, see [1] and [2] in the FAQ.

> Any suggestions re how else to get the backtrace you desire, or any other info that might be helpful?

You may be able to get something useful using the JIT debugger, by setting the error_start token in the CYGWIN env var, prior to invoking the command which crashes, e.g.

CYGWIN="error_start=C:\cygwin\bin\dumper"
CYGWIN="error_start=C:\cygwin\bin\gdb"


> The below were run within a shell within Emacs running on an X server other than :0.  The behavior looks the same as when running in a Windows CMD shell, except here the XWin output seems to be printing locally rather than going to XWin.0.log.  The "@@@@@@@"s are hand-edited whiteouts.
> 
> The note below about Zonealarm is "interesting".  No Zonealarm, tho do have McAfee's firewall enabled.

Apparently cygcheck detects ZoneAlarm by looking for the registry key "SYSTEM\\CurrentControlSet\\Services\\vsdatant", or the file "%windir%\\System32\\vsdatant.sys".

> The run under gdb seemed to startup ok; I closed up X after a little while via "Exit..." on the taskbar icon.

[1] http://x.cygwin.com/docs/faq/cygwin-x-faq.html#q-fork-failures
[2] http://cygwin.com/faq-nochunks.html#faq.using.bloda

-- Jon TURNEY
Volunteer Cygwin/X X Server maintainer


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