Messages in this thread | | | Date | Sat, 08 Mar 2008 01:08:46 -0600 | From | Frank Sorenson <> | Subject | Re: 2.6.25-rc4 OOMs itself dead on bootup |
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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
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