Mike Frysinger wrote:
> On Tuesday 03 June 2008, Bernard Blackham wrote:
>> When I switched from udev+udevd to mdev, booting was much faster and it
>> shaved a decent amount from the total image size. However, I've recently
>> noticed device nodes sometimes disappearing on boot.
>
> this is a known corner case and will always be there. it's why the kernel
> guys have deprecated the hotplug exec mechanism in favor of netlink sockets.
> the only real solution is a daemon + netlink. neither of which are desirable
> in mdev. everything else is a workaround.
Ah k. Thanks for clearing that up :)
> feel free to contribute a mdevd ;).
Having glanced through udevd.c, I'm rapidly reaching the conclusion that
for busybox, a simple mdevd that did the following would suffice:
- listen for an event on netlink
- when an event arrives, dispatch it to udev (internally even, without
forking)
- wait for completion (queue up other incoming messages if waiting for
an external program)
- lather, rinse, repeat
No control interface, no event queuing, no process throttling, etc.
There's a lot of extra complexity in udevd - e.g. using a queue
mechanism which I gather is to support parallel runs of udev when they
can be accomodated. If this, along with the control interface were to be
dropped (kill -9 is a control interface to me ;) then I imagine the
resulting mdevd would be pretty simple, very small and just as functional.
Would this be all it takes? Anyone with more than half an hour's
experience of looking at udev's source code willing to comment? :)
Regards,
Bernard.
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