> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Frank Sorenson wrote:
> > I did some additional debugging, and I believe you're correct about it
> > being specific to my system. The system seems to run fine until some
> > time during the boot. I booted with "init=/bin/sh" (that's how the
> > system stayed up for 9 minutes), then it died when I tried starting
> > things up. I've further narrowed the OOM down to udev (though it's not
> > entirely udev's fault, since 2.6.24 runs fine).
> >
> > I ran your debug info tool before killing the box by running
> > /sbin/start_udev. The output of the tool is at
> >
http://tuxrocks.com/tmp/cfs-debug-info-2008.03.06-14.11.24
> >
> > Something is apparently happening between 2.6.24 and 2.6.25-rc[34] which
> > causes udev (or something it calls) to behave very badly.
>
> Found it. The culprit is 8f47f0b688bba7642dac4e979896e4692177670b
> dcdbas: add DMI-based module autloading
>
> DMI autoload dcdbas on all Dell systems.
>
> This looks for BIOS Vendor or System Vendor == Dell, so this should
> work for systems both Dell-branded and those Dell builds but brands
> for others. It causes udev to load the dcdbas module at startup,
> which is used by tools called by HAL for wireless control and
> backlight control, among other uses.
>
> What actually happens is that when udev loads the dcdbas module at
> startup, modprobe apparently calls "modprobe dcdbas" itself, repeating
> until the system runs out of resources (in this case, it OOMs).
>
> # ps axf
> ...
> 506 ? S 0:00 /bin/bash /sbin/start_udev
> 590 ? S 0:00 \_ /sbin/udevsettle
> 533 ? S<s 0:00 /sbin/udevd -d
> 629 ? S< 0:00 \_ /sbin/udevd -d
> 630 ? S< 0:00 | \_ /sbin/modprobe
> dmi:bvnDellInc.:bvrA08:bd04/02/2007:svnDellInc.:pnMP061:pvr:rvnDellInc.:rn0YD479:rvr:cvnDellInc.:ct8:cvr:
> 949 ? S< 0:00 | \_ /sbin/modprobe dcdbas
> 950 ? S< 0:00 | \_ /sbin/modprobe dcdbas
> 951 ? S< 0:00 | \_ /sbin/modprobe dcdbas
> 953 ? S< 0:00 | \_ /sbin/modprobe dcdbas
> 955 ? S< 0:00 | \_ /sbin/modprobe dcdbas
> 958 ? S< 0:00 | \_
> /sbin/modprobe dcdbas
> ...repeat...
>
> When the system crashed, there were at least 11,600 instances of
> "/sbin/modprobe dcdbas", each calling the next.
>
> Reverting 8f47f0b lets the system boot up just fine again. Note that a
> manual "modprobe dcdbas" also causes this recursive behavior, it's just
> not forced on the system by udev.
>
> So dcdbas is a regression from 2.6.24, as well as being broken in other
> ways.
>
> Frank
> - --
> Frank Sorenson - KD7TZK
> Linux Systems Engineer, DSS Engineering, UBS AG
>
frank@tuxrocks.com
