On Thu, 2011-09-15 at 13:29 +0200, Thomas Schmitt wrote: > Hi, > > i am upstream developer of libburn and CD/DVD/BD burn program xorriso. > It seems urgent that i coordinate the activities of libburn with the > activities of udev. > > What is the recommended way for a library resp. a console program > to tell udev, that a CD drive and the media will undergo arbitrary > changes and should not be accessed during that time ? There isn't one. And I don't see any reason why udev should try to reidentify a CD drive on a 'change' event. I mean, it's not exactly likely to change itself to be capable of handling a new disc format that would deserve an additional symlink name. [...] > On an installation of Debian GNU/Linux 6.0.2 amd64, /dev/dvdrw vanishes > if libburn loads the tray. It comes back only if some other program run > uses the /dev/sr device file to which the link should point. I assume the other symlinks to this device also disappear? [...] > The vanishing link is accompanied by these messages in /var/log/daemon.log : > ------------------------------------------------------------------ > > Sep 9 22:00:41 debian2 udevd[435]: seq 1274 queued, 'change' 'scsi' > [...] > Sep 9 22:00:41 debian2 udevd-work[21697]: 'cdrom_id --export /dev/sr0' started > Sep 9 22:00:41 debian2 cdrom_id[21698]: custom logging function 0x7f17909c9010 registered > Sep 9 22:00:47 debian2 cdrom_id[21698]: unable to open '/dev/sr0' > Sep 9 22:00:47 debian2 udevd-work[21697]: '/lib/udev/cdrom_id' (stderr) 'unable to open '/dev/sr0'' > Sep 9 22:00:47 debian2 udevd-work[21697]: 'cdrom_id --export /dev/sr0' returned with exitcode 1 > [...] > Sep 9 22:00:48 debian2 udevd-work[21697]: update old name, '/dev/dvdrw' no longer belonging to '/devices/pci0000:00/0000:00:11.0/host2/target2:0:0/2:0:0:0/block/sr0' > Sep 9 22:00:48 debian2 udevd-work[21697]: no reference left, remove '/dev/dvdrw' > [... no attempt to create a new /dev/dvdrw ...] > Sep 9 22:00:48 debian2 udevd[435]: seq 1275 done with 0 > > ------------------------------------------------------------------ > > It looks as if xorriso's activities block the drive while udev is trying > to get access to it in the time between 22:00:41 and 22:00:47. [...] Right. Ben. -- Ben Hutchings All extremists should be taken out and shot.
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