On Tue, 18 Apr 2006, Andreas Jellinghaus wrote: > I tried once more, and this time with /dev/bus/usb only. > > How can there be five processes with the same file opened? > > [EMAIL PROTECTED]:~# lsof |grep /dev/bus/ > ifdhandle 26749 root 3u CHR 189,273 > 51693 /dev/bus/usb/003/018 > ifdhandle 26761 root 3u CHR 189,273 > 51693 /dev/bus/usb/003/018 > ifdhandle 26765 root 3u CHR 189,273 > 51693 /dev/bus/usb/003/018 > ifdhandle 26775 root 3u CHR 189,273 > 51693 /dev/bus/usb/003/018 > ifdhandle 26819 root 3u CHR 189,273 > 51693 /dev/bus/usb/003/018 > [EMAIL PROTECTED]:~# > > all of them open it with O_EXCL? > > does O_EXCL not work standalone? should I use flock or something like > that instead to prevent several processes accessing the same file? > Or are usb device file somehow special and those methods do not work?
Take a look at "man 2 open". It says that O_EXCL doesn't do anything unless you use it along with O_CREAT, in which case you get an error if the file already exists. So I guess you really don't want to use O_EXCL. You should look at the man pages for flock, fcntl, and lockf. Alan Stern ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
