hotplug and test and set

[Rainer Dorsch <rdorsch@web.de>]

Hello,

I have an Epox DG02A usb dongle for bluetooth.

$ ls usbview
[...]
Bus 003 Device 002: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle


I added a script to start pand into my /etc/hotplug.d/usb directory on my 
Debian system. 

rd@topsi:~$ cat /etc/hotplug.d/usb/epox-bluetooth.hotplug
#!/bin/sh
pidfile=/var/run/pand.pid
lockfile=/var/lock/pand.lock
DAEMON=/usr/bin/pand
case `echo $PRODUCT|cut -d / -f 1-2` in
        # a12/1/525 and a12/1/828 have been seen for the Epox BT DB02A
        a12/1) break ;;
        *) exit ;;
esac
case $TYPE in
        224/1/1) break ;;
        *) exit ;;
esac
case $ACTION in
        add)
            # poor man's locking
            if [ ! -e $lockfile ]; then
              touch $lockfile
              echo entered locked area >> /tmp/epox.log
              hcitool scan >> /tmp/epox.log
              sleep 1
              start-stop-daemon --start --exec $DAEMON -- --nodetach --role 
PANU --search --encrypt --pidfile $pidfile
            fi
            ;;
        remove)
            start-stop-daemon --stop --exec $DAEMON --pidfile $pidfile
            rm $lockfile
            ifdown bnep0
            ;;
esac
rd@topsi:~$


My problem is that this script is called four times when the dongle is plugged 
in. I order to avoid to call pand four times, I added a poor test and set to 
the script to add a lock when a pand is running. Does anybody know, what I 
could do to get a better locking behaviour, e.g. an atomic test and set?


Many thanks,
Rainer

-- 
Rainer Dorsch
Alzentalstr. 28
D-71083 Herrenberg
07032-919495
Icq: 32550367


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