[systemd-devel] Antw: Re: how to debug kernel panic which generated by udevadm at systemd?

[www]

Dear Mantas and Ulrich,


Thank you very much for your help. Because systemd will automatically call this driver, which causes the system to fail to start normally, I have to load the driver in a different way (load it separately), and then debug it. Thanks again for your help.


thanks,
Byron



At 2019-10-16 14:12:35, "Ulrich Windl" <Ulrich.Windl at rz.uni-regensburg.de> wrote:
>>>> Mantas Mikulenas <grawity at gmail.com> schrieb am 15.10.2019 um 20:32 in
>Nachricht
><CAPWNY8Whzf+G6AWBkHTLFAXUo=fRm_VtqO+i1tYt-yaobOCU8g at mail.gmail.com>:
>> On Tue, Oct 15, 2019 at 3:02 PM www <ouyangxuan10 at 163.com> wrote:
>> 
>>> Dear all,
>>>
>>> I add a new driver to kernel, and it probe success. When enter into
>>> systemd, the udevadm generate a kernel panic.
>>> I want to ask how to debug it and find out where the error occurred? When
>>> did udevadm load? What commands are used by udevadm, and what are the
>>> specific operations?
>>>
>> 
>> There aren't many udevadm calls in systemd... The main one is
>> systemd-udev-trigger.service, which calls `udevadm trigger
>> --type=subsystems --action=add`, then repeats the same for type=devices. It
>> tries to generate coldplug uevents by writing 'add' to each found device's
>> /sys/.../uevent file.
>
>That's waht I guessed: The driver being loaded created siome udev event (with
>probably invalid data in it), so when processing those, problems are
>triggered.
>
>I'm not arguing whether all thge components involved are robust enough (to
>avoid a kernel panic), but is there a kind of "driver validation tool" (like
>inserting the module, querying it's metedata, udev events, removing the module
>again, etc.)?
>
>
>Regards,
>Ulrich
>
>> 
>> (The second is systemd-udev-settle.service, but it is disabled by default
>> on most systems and just waits for udev's job queue to empty.)
>> 
>> -- 
>> Mantas Mikulėnas
>
>
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