freenx-team team mailing list archive

[Thilo Uttendorfer <t.uttendorfer@xxxxxxxxxxxx>]

Hi Jeremy,

On Monday 27 April 2009, Jeremy Wilkins wrote:
>  I'm confused as to what this trap and loop accomplish. We can't paste code
> in until we understand the ramifications of the changes.

> > After some more debugging and testing I finally solved the problem. When
> > cmd_node_smbmount (as well as cmd_node_addprinter) is called, the
> > function gets instantly terminated (at least in my setup/environment)
> > because it was not properly detached.
> >
> > I had to add several things to the cmd_node_smbmount call:
> > - Use "double fork" (thanks to [1])
> > - Use trap
> > - Close all open file handles


I try to explain it a bit more detailed:

- The "double fork" is used to make sure the process outlives the current
  shell. I thought this was necessary to detatch the process, but after
  running another test, it works without the extra parentheses as well.
  Updated patch attached.
- The trap command is used to catch signal 1 (SIGHUP), otherwise the process
  terminates.
- The loop is used to close all open file handles. freenx uses some exec calls
  like "exec 4>&1" but closes only STDIN, STDOUT and STDERR ( "exec 0<&-",
  "exec 1>&-", "exec 2>&-" ). Maybe it's too much to close all open file
  handles up to 255 (probably only a few are used), but it doesn't harm
  either. Anyway, if you don't close these file handles, the process hangs.


Thilo

-- 
Thilo Uttendorfer
Linux Information Systems AG
Putzbrunner Str. 71, 81739 München

t.uttendorfer@xxxxxxxxxxxx, http://www.linux-ag.com

--- nxnode.orig	2009-04-09 16:00:02.000000000 +0200
+++ nxnode	2009-04-28 18:37:43.000000000 +0200
@@ -1560,10 +1560,10 @@
 		cmd_node_suspend
 	;;
 	--smbmount)
-		cmd_node_smbmount &>/dev/null </dev/null &
+		trap '' 1; for ((i=3; i<255; i++)); do eval "exec $i<&- $i>&-"; done; cmd_node_smbmount &>/dev/null </dev/null &
 	;;
 	--addprinter)
-		cmd_node_addprinter &>/dev/null </dev/null &
+		trap '' 1; for ((i=3; i<255; i++)); do eval "exec $i<&- $i>&-"; done; cmd_node_addprinter &>/dev/null </dev/null &
 	;;
 	--check)
 		echo "NX> 716 finished"