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Date: Fri, 28 Jun 2013 10:41:57 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Failure with fork()
Message-ID: <20130628084157.GP2378@calimero.vinschen.de>
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References: <alpine DOT DEB DOT 2 DOT 02 DOT 1306272257220 DOT 27492 AT enira DOT zlyna DOT ubzr> <51CD4177 DOT 1040708 AT gmail DOT com>
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User-Agent: Mutt/1.5.21 (2010-09-15)

On Jun 28 09:55, marco atzeri wrote:
> Il 6/28/2013 8:42 AM, Alan W. Irwin ha scritto:
> >I am getting absolutely nowhere.
> >
> [cut]
> >
> >I didn't get these hangs a month ago when I tried all this
> >before with wine-1.5.19.  Instead, at that time I got the exact error
> >message when running the above script concerning an unhandled page
> >fault that others have described at
> >http://bugs.winehq.org/show_bug.cgi?id=24018 and which the fork-fixed
> >cygwin1.dll is supposed to fix.  So presumably Cygwin's
> >bash.exe or some application executed by the above script has
> >changed in the last month to cause the different wine symptoms.
> >Or I am inadvertently doing something different than I did a month
> >ago.
> >
> >So unless someone can suggest a method to get around the "Can't open
> >package database for writing.  File exists." message, and assuming
> >that method doesn't subsequently run into the script hang (which is a
> >big if), then I think it is time for someone with a lot more wine and
> >cygwin expertise than me to take over here to attempt to try and
> >figure out a way to run setup.exe on Wine with fork-fixed cygwin1.dll
> >overwriting the buggy version.
> >
> >Alan
> 
> Hi Alan,
> I assume you are not testing on wine for fun, but cygwin on wine
> seems a real problem as the bug can be in any of the two platforms.

I think it's a misconception that this very bug is the culprit of
Cygwin not running under wine.  Here's why:

What this bug did was very simple.  On each fork, the child process
committed 4K more stack than its parent.  The default stacksize for the
main thread of a process is 2 Megs.  It's a long way for a process to
take that much space on the stack.  So this problem should be visible
only in rare circumstances wher the main thread of a parent process
is already filled and then the child crashes because the 2 Megs are
overrun.  As I mentioned in my first post to this thread, the testcase
took almost 500 forks until the problem occured, 485 to be exact.
485*4K = 1.9 Megs.

If anything keeps Cygwin from running under Wine, it's probably some
different problem, which still need investigating.

> Could you clarify the original scope ?
> Eventually we can test in your behalf.
> 
> As alternative to wine, if I am not wrong, Corinna when testing
> cygwin on several platforms (32/64, XP, W7, W8 , Server...)  is
> using some VM

Yes, I'm running VMs using Qemu/KVM with each Windows version since NT4
as guests.  Of course, that doesn't mean Cygwin should not run under
Wine, but it's not exactly a pressing issue from my POV.  I appreciate
any debugging efforts, but that probably requires somebody more fluent
with Wine internals.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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