linux-kernel - Re: [2.6.26] kobject_add_internal failed for 2:0 with -EEXIST / unable to handle kernel NULL pointer dereference in sysfs_create

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Date:	Wed, 29 Oct 2008 22:51:14 +0100
From:	"Kay Sievers" <kay.sievers@...y.org>
To:	"Folkert van Heusden" <folkert@...heusden.com>
Cc:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org
Subject: Re: [2.6.26] kobject_add_internal failed for 2:0 with -EEXIST / unable to handle kernel NULL pointer dereference in sysfs_create_link

On Wed, Oct 29, 2008 at 16:25, Folkert van Heusden
<folkert@...heusden.com> wrote:
>> >> >> > While running my http://vanheusden.com/pyk/ script (which randomly
>> >> >> > inserts and removes modules) I triggered the folllowing oops in a 2.6.26
>> >> >> > kernel on an IBM xSeries 260. This oops (in fact no oops at all) did not
>> >> >> > get triggered in a 2.6.18 kernel on that system.
>> >> >> >
>> >> >> > [   42.507375] FDC 0 is a National Semiconductor PC87306
>> >> >> > [   42.509057] kobject_add_internal failed for 2:0 with -EEXIST, don't try to register things with the same name in the same directory.
>> >> >> > [   42.509291] Pid: 5301, comm: modprobe Not tainted 2.6.26-1-amd64 #1
>> >> >> > [   42.509431]
>> >> >> > [   42.509433] Call Trace:
>> >> >> > [   42.509685]  [<ffffffff8031b031>] kobject_add_internal+0x13f/0x17e
>> > ...
>> >> >> > [   42.511519]  [<ffffffff8027d23b>] bdi_register+0x57/0xb4
>> >> >>
>> >> >> Looks like bdi sees two devices with the same devnum, or didn't
>> >> >> cleanup an old entry. What does: ls -l "/sys/class/bdi/" print?
>> >> >
>> >> > The following:
>> >> > folkert@...iantesthw:~$ ls -l /sys/class/bdi/
>> >> > drwxr-xr-x 3 root root 0 2008-10-28 18:32 2:0
>> >> > drwxr-xr-x 3 root root 0 2008-10-28 18:32 2:1
>> >>
>> >> Oh, you are running the old sysfs layout without symlinks. Care to
>> >> tell where the "device" link in these directories points to?
>> >
>> > None exist:
>> > folkert@...iantesthw:~$ ls -la /sys/class/bdi/*/device
>> > ls: cannot access /sys/class/bdi/*/device: No such file or directory
>>
>> Ah, sorry. Seems the bdi stuff never got to pass the usual parent
>> device with the device registration, to let the bdi device show up at
>> the right place in the device tree.
>>
>> Let's see what current devices on your box have the major 2:
>>   find /sys -name dev | xargs grep '^2:'
>
> /sys/block/fd0/dev:2:0
> /sys/block/fd1/dev:2:1
>
> As my script does modprobe/rmmod in parallel (4 processes) maybe it is a
> conflict of one process doing an modprobe of floppy while the other does
> an rmmod? Or both a modprobe?

Might be, yes. If you just bootup, and don't run your modprobe/rmmod
script, does the box have 2 floppy devices in /sys too?

Kay
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