Hey Alan,
On Tue, Feb 19, 2019 at 01:06:17PM -0500, Alan Altmark wrote:
> On Tuesday, 02/19/2019 at 01:49 GMT, Benjamin Block <bbl...@linux.ibm.com>
> wrote:
> > udev_timeout=30
> >
> > The default is 30s, you can add it to the kernel command line
> > (/etc/zipl.conf), and increase it (e.g.: udev_timeout=90).
> >
> > This will increase the timeout for for both udevadm and the step where
> > it waits for the root-volume to appear.
>
> Does that mean ALL of the needed needed LUNs must be brought online within
> 30 seconds? Or that REPORT LUNS (LUN 0) or INQUIRY (LUN 0 and/or all
> others) must EACH respond within 30 seconds?
>
It regulates two things at once.
First, during the early phase of the INITRD, the init process will start
'udev', and then use 'udevadm settle --timeout=${udev_timeout}' to wait
till it udev processed all the events happening in the kernel (such as
adding devices, executing rules upon it saw specific devices being added
[such as loading drivers and so on], and so on). This timeout is
deceptive though, it will only wait up to this amount OR if there is no
events in the queue anymore.. if an event happens 1s after it already
stopped waiting, bad luck - although, because udev keeps running as
daemon, it should sill process the event if I am not mistaken, its just
that init will continue doing other things meanwhile (such as:).
The second mechanism it controls is the late phase during run of the
INITRD, where init will wait till it sees the root-volume appear. In
this phase it will wait up to ${udev_timeout} seconds till it sees it,
and after that it will fall back to ask the user for guidance (which is
what I think is happening here, although strictly spoken, this is only a
guess).
That is as far as I have read the code - mind you, I didn't write it, so
it may well be that I have miss-interpreted something.
But this all changes with SLES12, because SLES12 uses a different kind
of INITRD (dracut) and the code there probably doesn't even know this
parameter. So this is strictly SLES11 only.
--
With Best Regards, Benjamin Block / Linux on IBM Z Kernel Development
IBM Systems & Technology Group / IBM Deutschland Research & Development GmbH
Vorsitz. AufsR.: Matthias Hartmann / Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen / Registergericht: AmtsG Stuttgart, HRB 243294
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