[Novalug] Bug: soft lockup.
Gary Knott
garyknott@gmail.com
Sun Jul 12 18:24:57 EDT 2015
We have a KDE Linux system with 2 disks; /home is
in /dev/sdb1 which is all of /dev/sdb as an ext3 filesystem.
/, swap, /boot is on /dev/sda
All of a sudden (and after an update of a few packages
that I paid no attention to) we can no longer
use this system: we get "Bug: soft lockup - CPU#1 stuck for 23s
[modprobe]" And there seems to be no way
around this. Googling tells us that modprobe is
running on CPU1 and is not relinquishing it!
When we stick in a knoppix disk, we do not have
this problem.
Someone said changing their power supply fixed this, but
as Knoppix runs, I am skepical.
I guess we will try to install a new Linux system on
/dev/sda and loose all configuations, alias's etc,
and special installed programs. Alas.
But my question is, can I take the /home drive, put it
in an LXDE Lubuntu system and mount it
- say as /odsk and read/write it? i.e. is there
any special stuff - disk label etc, I am going to
have to know about it?
sub-question 1: I think I plug the old drive in, and then
boot and login. Then I edit /etc/fstab and add a line for this
disk, copying how the other disk was specified, giving the
"mount-point" /odsk. Then I do [cd / and mkdir odsk],
and then give the command [mount /odsk] - all as root of course,
and I'm ready to read/write in /odsk/home/user/...
Is that right?
sub-question 2: When I shutdown and
then reboot, will the added disk be there under /odsk
and ready?
sub-question number 3: If I pull the added disk back out,
and reboot with a /etc/fstab entry for it, what will
happen? My guess is Linux will hang for awhile
looking for this device and then give-up and keep
booting, ignoring that fstab entry. Is that right?
sub-sub-question 3.1 If I remove the added disk
while running ( a "hot" unplug,) what will happen?
Will the OS pay no attention as long as I never
mention /odsk? (Of course I'm not going to do this, I
just want to know how Linux handles it.)
subquestion 4: Can I now put the disk back in
and boot and find the disk under /odsk as before?
penultimate question: I think modprobe is used
to locate a "device driver" module and load it into
kernel space. how can I find out what device
modprobe is hanging for? (modem, speakers, CD-drive, etc?
This is an old machine, circa 2003?.)
If it is some non-essential device, I could just remove it, and
see if I can boot. But more to the point what's the
cause of the failure?
final question: Does anybody know what else
I could do about this kernel bug? (There are some short
googlable writeups explaining that this is really a kluge
in linux with a special process devoted to checking
for other processes that don't relinquish a cpu in a timely manner.
Is there any reason to think the power supply or a capacitor
could be the cause?
Thanks, gary knott, knott@civilized.com
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