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SubjectRe: (reiserfs hang at boot) where is the kernel debugger?
Rik van Riel wrote:

> > How broken is it? I have a test9-pre7 system that's exhibits an
> > elusive bug, reiserfs hangs at boot time, and all I need is a
> > backtrace on the D state processes.
>
> Could be a VM bug. ;)

It could, but I strongly doubt it. We've seen this bug [very] infrequently
for the last year. I managed to build a system and trigger it four out of
five times on boot. Frustratingly after adding kdb, I'm only able to
trigger it once in ~20 boots now.

I'm rather hesitant to trust my findings, kdb says all the processes are in
schedule+nn. Yes, it can be related but I'm a wee bit dubious. I'd post
all my trace findings but I really don't want to cross type all that right
now -- I left my serial cable at the office. I'll post the traces
tomorrow. The simple version of them is as follows:

PC: schedule()
-1: down()
-2: down_fail()
...

Some processes have devfs calls following this, some have typical kernel
init calls etc., but the common factor in all of them is they all sit in
schedule and they all have the same PC location. SysRq-T shows C111914B
which is outside system.map but again I'm dubious. During normal operation
of the machine, -T shows processes having PCs of 0x00000000 and 0x7f000000
which strikes me as a bit odd.
For e.g. the following:

sshd S 7FFFFFFF 0 247 88 248 (NOTLB)
121
sig: 0 0000000000000000 0000000000000000 : X
bash S 00000000 0 248 247 263 (NOTLB)
sig: 0 0000000000000000 0000000000010000 : X
BTW, if nobody has any qualms, I'm going to poke at this output and tidy it
up, the header is disjointed from the body.

-d

--
"There is a natural aristocracy among men. The grounds of this are
virtue and talents", Thomas Jefferson [1742-1826], 3rd US President


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