issue with 243-pre8: strange userland/proc breakage

[Martin Diehl]

Hi,

Something not so obvious (at least for me ;-) seems to be broken in
userland. Could narrow it down to triggers like failing sed, for example
(from /etc/rc.d/init.d/usb)

PKLVL=`sed 's/^\(.\).*/\1/' < /proc/sys/kernel/printk`

Another probably related thing happens when rc.sysinit sed's from
/proc/cmdline.

Common in both cases:
sed operation from /proc-tree, no error from sed, but failed to work as
expected - i.e. instead of returning the first character/number from
kernel.printk sysctl it returns empty string. For 2.4.0 it is ok.
Simple "cat /proc/sys/kerl/printk" doesn't show any difference.

symptoms:
- Box hangs at rc.sysinit when broken "sed ... /proc/cmdline" tries to
  start linuxconf. Probably some kind of deadlock: all processes sleeping,
  according to SysRq: PC always in cpu_idle. Hitting SAK solves the
  issue: booting finishes without any observable degradation.

- "Malformed setting kernel.printk=" error message from sysctl(8) when
  starting/stopping usb. No harm, simply fails playing games with
  kernel.printk.

System is K6-II UP. Using egcs-2.91.66 or gcc-2.95.3(pre) doesn't make any
difference. Playing with .config to exclude fb(ati64), devfs, scsi, bttv,
usb didn't change anything either.
Unfortunately the step from 2.4.0 is quite big and I had no time yet to
narrow it down - going to try later.

Regards
Martin