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udev event completion order (was: Re: Debian Installer team monthly meeting minutes (20051214 meeting))

[CC'ing hotplug-devel]

I demand that Marco d'Itri may or may not have written...

> On Dec 17, Christian Perrier <bubulle@debian.org> wrote:
>> It is currently very likely that systems with two network interfaces will
>> end up with both switched on the installed system after the reboot. This
>> is of course a blocker.

>> The discussion showed that sticking with discover while udev is used may
>> be the main reason for this.

> No. This will happen no matter how the system was installed, because
> modules are loaded concurrently and the first one to finish its setup wins.
> This applies to the /dev/cdrom and similar links on systems with multiple
> CD readers too.

FWIW, I've seen this with both CD/DVD drives and both sound devices in one of
my machines. I have no doubt that the same applies to DVB cards etc., which
might cause problems when one's DVB-T and another's DVB-S or something.

> The solution so far appears to be writing a rules file which will
> statically assign the names.

An alternative appears to be to process events in series... or maybe delaying
naming until all modules have been loaded could help? I think that ordering
by bus address or kernel device name could help here.

Of course, adding some modules may trigger another round of events, causing
more modules to be loaded, but this shouldn't be a problem - it should be
just another batch of events to be buffered and processed after the current
batch is complete.

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