[systemd-devel] systemd-udev causes slow boot and high load

Lennart Poettering lennart at poettering.net
Tue May 19 03:37:05 PDT 2015

On Tue, 19.05.15 12:02, Marco Steinacher (mailinglists at websource.ch) wrote:

> Hi,
> After upgrading my system to Debian jessie and switching to systemd I
> have the following problem:
> 1. During boot there is the message
> [    **] A start job is running for udev Wait for Complete De...on (11s
> / 3min)
> after "systemd-fsck[452]: /dev/sda5: clean" and it takes about 2 minutes
> until the boot process continues.
> systemd-analyze blame shows:
>   2min 2.945s systemd-udev-settle.service

systemd-udev-settle.service just waits for devices to be probed. It
will wait for the kernel drivers to initialize and the udev rules to
be pliugged in.

In fact, there's really no need to have this in the boot process at
all, unless you are using some broken software that assumes that
there's a point in time where all hardware has been plugged in, but
such a point in time does not actually exist, and hasn't existed in a
long time (simply because USB and other busses can take any time they
want before initialization is complete and the devices have shown up).

> 2. dmesg also shows:
> [  254.305831] INFO: task systemd-udevd:296 blocked for more than 120
> seconds.
> [  254.305962]       Not tainted 3.16.0-4-686-pae #1
> [  254.306069] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
> [  254.306165] systemd-udevd   D 00000000     0   296    234 0x00000004
> and similar messages for the tasks systemd-udevd:308 and
> systemd-udevd:307. The messages repeat a couple of times (see full log
> below).

There you go: your kernel is hung, some driver or your xen irq
handling is borked and hangs during initialization. This is a kernel
problem, please report this to the kernel bugzilla.


Lennart Poettering, Red Hat

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