Recursive locking complaint with nvme-5.13 branch

[Bart Van Assche]

On 4/1/21 9:12 AM, Christoph Hellwig wrote:
> We've seen a similar trace a while ago, and back then decided not to
> fix it given that it is harmless and pktcdvd was considered to be on the
> way out.  But it seems like systemd now tries to set up pktcdvd?

Hi Christoph,

The following snippet from the system log shows that the call trace was
indeed triggered by setting up the pktcdvd driver:

Mar 31 20:55:10 ubuntu-vm kernel: pktcdvd: pktcdvd0: writer mapped to sr0
Mar 31 20:55:10 ubuntu-vm kernel: Adding 8388604k swap on /dev/sdc.  Priority:-2 extents:1 across:8388604k
Mar 31 20:55:10 ubuntu-vm kernel:
Mar 31 20:55:10 ubuntu-vm kernel: ============================================
Mar 31 20:55:10 ubuntu-vm kernel: WARNING: possible recursive locking detected
Mar 31 20:55:10 ubuntu-vm kernel: 5.12.0-rc3-dbg+ #6 Not tainted
Mar 31 20:55:10 ubuntu-vm kernel: --------------------------------------------

The following information is also relevant:

root at ubuntu-vm:~# lsscsi | grep sr0
[3:0:0:0]    cd/dvd  QEMU     QEMU DVD-ROM     2.5+  /dev/sr0

bart at ubuntu-vm:~$ cat /lib/udev/rules.d/80-pktsetup.rules
# Create and remove packet writing device for each optical block device
ACTION=="add", SUBSYSTEM=="block", ENV{ID_CDROM}=="1", RUN+="/usr/sbin/pktsetup %E{MAJOR}:%E{MINOR}"
ACTION=="remove", SUBSYSTEM=="block", ENV{ID_CDROM}=="1", RUN+="/usr/sbin/pktsetup -d %E{MAJOR}:%E{MINOR}"

In other words, every time a CD-ROM is detected the above udev rule runs the
pktsetup executable.

I haven't found any udev rule in the systemd git repository that runs pktsetup.
I think it comes from the udftools repository.

Please let me know if you need more information.

Bart.