misc/131290: How to completely freeze FreeBSD 7.1 under a non-privileged user

[Mikolaj Golub]

On Thu, 05 Feb 2009 21:23:16 +0200 Mikolaj Golub wrote:

> On Thu, 5 Feb 2009 07:51:31 -0800 Sergey S wrote:
>
>  SS> Hello.
>
>  >> I can't hang the system running many cycles of loop.sh...
>
>  SS> :(
>
>  SS> I've no idea, what can be done in order to elucidate the problem...
>
> When I went home I left the machine with loop.sh run and now it is not
> pingable, so it looks like it hangs :-) Tomorrow, I will know this for sure.
>
> I noticed from your top output that your system was idle when you did your
> test while mine was rather loaded. That is why, I suppose, it required more
> time for me to hang it.

Yes, it hanged. I added to the GENERIC kernel config the followin options:

options     INVARIANTS
options     INVARIANT_SUPPORT
options     WITNESS
options     DEBUG_LOCKS
options     DEBUG_VFS_LOCKS
options     DIAGNOSTIC

options KDB
options DDB

and run script on idle system. The system froze on the second cycle run. It
did not panic and I was not able to enter the debugger, so no crush dump is
available.

Then I changed the scheduler to 4BSD. It hangs with 4BSD too but it looks like
it requires more cycles. When it froze first time with 4BSD I managed to enter
debugger pressing Ctr-ALt-ESC. But I made silly thing, I decided to check if
the system would resume to normal state if I just return from the debugger. It
did not and I was not able to enter ddb again. After this I hanged the system
several times to try to enter ddb but without success :-(

-- 
Mikolaj Golub