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Re: Problems with executing X11 programs via ssh

Hi Chris...

I understand your frustration...BUT please also consider my perspective.

The situation is that I traced the problem as far as I could (which was 
already a significant amount of work). What I found was that the "central" 
select call in the ssh client hangs (never returns) after the fourth or 
fifth call (it was repeatable--I just don't recall now) when (and only when) 
the ssh client had forked off into the background (using the -f option).

What I found while trying to track it down was that if I added a one second 
timeout to the select call to force it to return, it did so...AND that there 
was data available, so it should have in fact returned wthout this timeout. 
I was unable to follow the flow through the Cygwin (note the lower case w) 
DLL with multiple processes.

So, for the time being, I put a one second timeout in the "central" select 
call of the ssh client. It was not too expensive, and it stoped the hanging. 
I reported my results to this list and Corinna commented that it did not 
look like a ssh bug (and thus a Cygwin bug).

When I see people with the same problem post on this list (ssh client 
hanging when using the -f option with a command), I offer this to 
help...because it "fixes the problem for now". I make my comment because I 
feel it is only a workaround.

Time permitting, I will learn more and dig deeper...but for now, this is the 
limit of my digging ability.

I too would like to see it fixed in the DLL. That is why I posted my results 
on this list. Specifically, the problem occurs (every time) with

ssh -f localhost sleep 30

on a win2k box with the current versions from setup.

Please let me know how I can be of further assistance.



>From: Christopher Faylor <>
>Subject: Re: Problems with executing X11 programs via ssh
>Date: Sat, 25 Aug 2001 14:16:32 -0400
>On Fri, Aug 24, 2001 at 08:15:15PM -0700, Karl M wrote:
> >Hi Earl...
> >
> >That looks like the problem I had. See my patch attached to the e-mail
> >titled
> >
> >ssh hanging with -f option--a workaround (July 27, 2001).
> >
> >on this list. This is not a proper is a workaround for what I
> >believe is a Cygwin bug that shows up in a select call after forking.
> >
> >I hope this helps. Let me (and the list) know if this fixes it for you.
>Of course, we never really have "proper fixes" from anyone here.
>"Workarounds" and speculation are a lot easier than applying brain power
>to actually fix a problem.
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