[THIN] Citrix MPS 4 and Cygwin

  • From: Adam Thompson <adwulf@xxxxxxxxx>
  • To: thin@xxxxxxxxxxxxx
  • Date: Fri, 23 Jan 2009 00:55:14 +0000

Dear all,

I've been experiencing a problem running an sshd on Citrix servers (PS
4 on Win2003 SP2) for quite a while now.

Usually, cygrunsrv.exe is run as a service, which spawns a child
process (sshd.exe).

On the Citrix PS 4 servers, it seems that cygrunsrv.exe cannot spawn
sshd.exe using fork().
The error is UNIX error #11 - which is "no more processes" - which
would suggest either PID exhaustion or virtual address space
depletion.  Yet neither of these conditions is evident on these
servers.  The commit charge is negligible, and it is perfectly
possible to launch new processes.

Occasionally, I can manually start the sshd service, but it terminates
around 5-10 minutes later, with no dump being created.

I have verified that the executables and libraries (eg cygwin1.dll and
sshd.exe) haven't had any memory optimization done on them, and in the
cases where they have done, I've rebased the cygwin DLLs and disabled
this feature - yet still I cannot run my ssh daemon.  The fork() call
is supposed to create an exact copy of the address space of the parent
process and give it to the child process, then return the PID to the
parent.  Does PS do anything which might prevent this?

I've not had much luck with procexp, filemon or regmon, and haven't
found anything interesting when manually killing cygrunsrv with
drwtsn32 to create a dump of the process memory.  I've asked on a
cygwin mailing list, and not had much luck with that.

Can anyone here think of anything on Citrix Presentation Server (or
XenApp if you prefer) which might prevent cygwin's fork() from
spawning the process, or failing to duplicate the address space of the
parent process?

Thanks in advance,

(a normally quiet subscriber to the list)
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  • » [THIN] Citrix MPS 4 and Cygwin - Adam Thompson