Bug#823980: udev: setting udev_log="debug" in /etc/udev/udev.conf == 90 second hang during boot

[Daniel Kahn Gillmor]

Package: udev
Version: 229-5
Severity: normal

I put udev_log="debug" into /etc/udev/udev.conf to try to understand
part of what udev is doing.  Then i needed to reboot my computer (for
other reasons).

Normal bootup is quite fast.  But right when the transition from the
initramfs to the regular system would normally happen, i see something
like this:

[***   ] (1 of 4) A start job is running for dev-sda1.device (16s / 1min 30s)

And it cycles through multiple "start jobs", each of them a .device
job.  after the designated timeout elapses, i'm given a chance to
enter into the emergency mode.  (even more problematically, on systems
where the keyboard is only available via USB, i can't enter the root
password or hit ^D to get past the emergency mode prompt).

From emergency mode, "systemctl default" brings up the system as
usual, with no problems.  If i remove udev_log="debug" from
/etc/udev/udev.conf and reboot, i don't have this hang on boot.

the systems i've tested this on all tend to use lvm, fwiw.  some of
them use encrypted volumes, some do not.  I haven't tested it on
systems without lvm yet.

My initramfs is built with dracut 044+38-1, using the standard debian
kernel hooks, in case it matters.  I see the issue when the system
udev.conf has the debug line in it -- it doesn't seem to matter
whether the udev.conf in the initramfs has the debug line or not.

not sure how to better understand or debug this (let alone fix it),
but i'm open to suggestions.

    --dkg

-- Package-specific info:

-- System Information:
Debian Release: stretch/sid
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.5.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages udev depends on:
ii  adduser      3.114
ii  dpkg         1.18.4
ii  libacl1      2.2.52-3
ii  libblkid1    2.28-1
ii  libc6        2.22-7
ii  libkmod2     22-1.1
ii  libselinux1  2.5-2
ii  libudev1     229-5
ii  lsb-base     9.20160110
ii  procps       2:3.3.11-3
ii  util-linux   2.28-1

udev recommends no packages.

udev suggests no packages.

Versions of packages udev is related to:
ii  systemd  229-5
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