[systemd-devel] [RFC][v3.13][v3.14][Regression] kthread:makekthread_create()killable

[Kay Sievers]

On Wed, Mar 19, 2014 at 4:54 PM, Joseph Salisbury
<joseph.salisbury at canonical.com> wrote:
> A kernel bug report was opened against Ubuntu[0]. We performed a kernel
> bisect, and found that a change introduced by upstream linux kernel
> commit 786235eeb introduced the bug as of v3.13-rc1.
>
> The bug indicates an issue with the SAS controller during
> initialization, which prevents the system from booting.
>
> There has been an on-going discussion on LKML[1] regarding this issue.
> It was found that this bug can be avoiding by increasing systemd-udevd's
> 30 seconds timeout.
>
> We were hoping to get some feedback from the systemd maintainers to see
> if it possible to increase the timeout to 120 seconds, or if there would
> be any possible complications with doing that?

Kernel modules should never take more than 30 seconds during loading.
The modprobe task is for *linking-in* modules into the kernel, not to
*run* unpredictable device initialization tasks; they should run
asynchronously, and modprobe should return as soon as the driver
itself is initialized, not the devices it drives.

You migh be able to work around the timeout with udev rules and
OPTIONS+="event_timeout=120", but that code was maybe never used or
tested, so it might not work correctly.

Thanks,
Kay