Re: 2.6.18-rc1-mm1

Michal Piotrowski
2006-07-10T09:22:40Z

Hi Ingo,

On 10/07/06, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Andrew Morton <akpm@osdl.org> wrote:
>
> > > This looks like a problem with cpufreq.
> > >
> > > =======================================================
> > > [ INFO: possible circular locking dependency detected ]
> > > -------------------------------------------------------
> > > cpuspeed/1426 is trying to acquire lock:
> > > (&inode->i_data.tree_lock){.+..}, at: [<c0151dc7>] find_get_page+0x12/0x70
> > >
> > > but task is already holding lock:
> > > (&mm->mmap_sem){----}, at: [<c0116cab>] do_page_fault+0x10d/0x4ea
> > >
> > > which lock already depends on the new lock.
> > >
> >
> > rofl. You broke lockdep.
>
> ouch! the lock identifications look quite funny :-| Never saw that
> happen before,

:)

> i'm wondering what's going on. Michal, did this happen
> straight during bootup? Or did you remove/recompile/reinsert any modules
> perhaps?

It's happening while /etc/init.d/cpuspeed execution.

I forgot about "make O=/dir/ clean". When new -mm is out I always
remove kernel directory and create new one.

>
> > Well. I guess it's barely conceivable that you earlier took an oops
> > while holding tree_lock, so lockdep decided that mmap_sem nests inside
> > tree_lock.
>
> Arjan is preparing a patch to turn off lockdep when we crash. Although i
> dont see any trace of an earlier oops in the dmesg.
>
> Ingo
>

Regards,
Michal

--
Michal K. K. Piotrowski
LTG - Linux Testers Group
(http://www.stardust.webpages.pl/ltg/wiki/)