Re: [BUG] fatal hang untarring 90GB file, possibly writeback related.

Chris Mason
2011-04-27T16:54:39Z

Excerpts from James Bottomley's message of 2011-04-27 12:50:00 -0400:
> On Wed, 2011-04-27 at 12:33 -0400, Chris Mason wrote:
> > Probably easier to debug with a sysrq-l and sysrq-w.
>
> Yes, just enabling them for the repro ... I didn't echo 1
> > /proc/sys/kernel/sysrq first time around
>
> > If you get stuck
> > on the filesystem, it is probably waiting on ram, which it probably
> > can't get because kswapd is spinning. Eventually everyone backs up
> > waiting for the transaction that never ends. If we're really lucky it
> > is just GFP_KERNEL where it should NOFS.
> >
> > Since you're often stuck in different spots inside shrink_slab, we're
> > probably not stuck on a lock. But, trying with lock debugging, lockdep
> > enabled and preempt on is a good idea to rule out locking mistakes.
> >
> > Does the fedora debug kernel enable preempt?
>
> No ... I've taken the Fedora 15 kernel config directly from their
> install CD for this (with a bit of munging to get it to work on -rc4)

Ok, I'd try turning it on so we catch the sleeping with a spinlock held
case better.

-chris