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

James Bottomley
2011-04-27T16:50:03Z

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)

James