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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Message-ID: <20081029152550.GT11214@vanheusden.com>
Date:	Wed, 29 Oct 2008 16:25:52 +0100
From:	Folkert van Heusden <folkert@...heusden.com>
To:	Kay Sievers <kay.sievers@...y.org>
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

> >> >> > 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?


Folkert van Heusden

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