** Description changed:
+ [Impact]
+ subsystems udev rules are not processed on boot, thus resulting in missing
devices on boot / before rootfs is mounted.
+
+ [Solution]
+ trigger udev subsystems and devices, in the initramfs, in that order.
+
+ [Testcase]
+ Boot s390x system with chzdev configured devices, and cio_ignore=all kernel
command line parameter. The chzdev configured devices should still be
discovered on boot.
+
+ [Original Bug report]
+
The udev initramfs-tools boot script does not trigger subsystem "add"
uevents. As a result, udev rules that listen to subsystem "add" events
are never activated. This problem exists on at least Ubuntu 16.04 and
17.10.
On s390, this results in a boot failure if the kernel is configured to
start with an active device black list (kernel parameter
cio_ignore=all,!condev). An example for an affected udev rule looks like
this:
- ACTION=="add", SUBSYSTEM=="subsystem", KERNEL=="ccw",
+ ACTION=="add", SUBSYSTEM=="subsystem", KERNEL=="ccw",
RUN{program}+="/bin/sh -c 'echo free 0009,ec30,ec32,f5f0-f5f2 >
/proc/cio_ignore'"
A proposed fix would be:
Modify /usr/share/initramfs-tools/scripts/init-top/udev:
Replace line
- udevadm trigger --action=add
+ udevadm trigger --action=add
with
- udevadm trigger --type=subsystems --action=add
- udevadm trigger --type=devices --action=add
+ udevadm trigger --type=subsystems --action=add
+ udevadm trigger --type=devices --action=add
This would also be consistent with the steps that the systemd udev
coldplug unit file performs (see /lib/systemd/system/systemd-udev-
trigger.service).
** Description changed:
[Impact]
subsystems udev rules are not processed on boot, thus resulting in missing
devices on boot / before rootfs is mounted.
[Solution]
trigger udev subsystems and devices, in the initramfs, in that order.
[Testcase]
Boot s390x system with chzdev configured devices, and cio_ignore=all kernel
command line parameter. The chzdev configured devices should still be
discovered on boot.
[Original Bug report]
The udev initramfs-tools boot script does not trigger subsystem "add"
uevents. As a result, udev rules that listen to subsystem "add" events
are never activated. This problem exists on at least Ubuntu 16.04 and
17.10.
On s390, this results in a boot failure if the kernel is configured to
start with an active device black list (kernel parameter
cio_ignore=all,!condev). An example for an affected udev rule looks like
this:
ACTION=="add", SUBSYSTEM=="subsystem", KERNEL=="ccw",
RUN{program}+="/bin/sh -c 'echo free 0009,ec30,ec32,f5f0-f5f2 >
/proc/cio_ignore'"
A proposed fix would be:
Modify /usr/share/initramfs-tools/scripts/init-top/udev:
Replace line
udevadm trigger --action=add
with
udevadm trigger --type=subsystems --action=add
udevadm trigger --type=devices --action=add
This would also be consistent with the steps that the systemd udev
coldplug unit file performs (see /lib/systemd/system/systemd-udev-
trigger.service).
+
+ [Regression Potential]
+ More udev rules will be now triggered, earlier, during initramfs stage of
boot rather than post-pivot-root. However, this is inline with current rootfs
behaviour and thus should not regress behaviour - simply some rules will get
triggered earlier.
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https://bugs.launchpad.net/bugs/1713536
Title:
udev: boot script does not trigger subsystem coldplug
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