Re: [PATCH] mdmonitor: check if udev has finished events processing

["Tkaczyk, Mariusz" <mariusz.tkaczyk@linux.intel.com>]

On 09.03.2021 15:52, Jes Sorensen wrote:
> On 3/9/21 6:17 AM, Tkaczyk, Mariusz wrote:
>> On 09.03.2021 10:45, Michael Fritscher wrote:
>>> Am 09.03.21 um 10:13 schrieb Wols Lists:
>>>> Is udev part of systemd? Are there alternate implementations for the
>>>> anti-systemd-holdouts? Iirc you don't need systemd itself to have udev,
>>>> but it might provoke a few screams ...
>>>>
>>>> My current (gentoo) system is OpenRC, but that's still on KDE4 and
>>>> hasn't been updated in a couple of years (don't ask why). My new system
>>>> is currently being built and is gentoo/systemd, but it's clear the
>>>> anti-systemd sentiment is still strong ...
>>>>
>>>> Cheers,
>>>> Wol
>>>>
>>>
>>> Good day,
>>>
>>> there is e.g. eudev ( https://wiki.gentoo.org/wiki/Project:Eudev ) with
>>> the explicit target to be used without systemd.
>>
>> It is a udev replacement and offers similar functionality.
>> I'm wondering on configuration without udev (systemd or other forks).
>> Is it still a case?
> 
> This is my main concern, small embedded devices that don't use systemd.
> I've never been a big systemd fan, but it's how the chips have fallen,
> so I am not overly worried about a couple of fanatics.
> 
> If eudev can do the trick, that would be great.
> 
> Cheers,
> Jes
> 
Hello,

Mdadm is in use in openwrt without udev (thanks to Artur for research).
They are using hotplug scripts:
https://openwrt.org/docs/guide-user/base-system/hotplug#coldplug
To provide compatibility with libudev dependency they wrote small shim:
https://openwrt.org/packages/pkgdata/libudev-fbsd
Unfortunately, not all libudev functions are defined, mdadm compilation
there might be problematic:
https://openwrt.org/packages/pkgdata_lede17_1/mdadm

Now, it makes sense to define libudev as optional dependency.
It should be done before new release, Intel will do that.

Anyway, I still think that we should drop udev detection from mdadm.
I there is no systemd-udevd, we should expect other tool to provide
similar functionality, like hotplug scripts, eudev.
IMO mdadm doesn't need to create any link.

Mariusz