Re: [PATCH] fix pgd_lock deadlock

Peter Zijlstra
2011-02-16T09:58:51Z

On Wed, 2011-02-16 at 00:17 +0100, Andrea Arcangeli wrote:
> On Wed, Feb 16, 2011 at 12:03:30AM +0100, Thomas Gleixner wrote:
> > I assume you run it with a lockdep enabled kernel as well, right ?
>
> Yes, I always run with lockdep and prove locking enabled on my test
> box, not sure how it's meant to trigger more bugs in this case, the
> debug check that should be relevant for this is DEBUG_VM and that is
> enabled too of course. I didn't try DEBUG_PAGEALLOC yet.

I think what Thomas tried to tell you is that your
VM_BUG_ON(in_interrupt()) is fully redundant if you have lockdep
enabled.

Lockdep will warn you if a !irqsave lock is taken from IRQ context,
since that is a clear inversion problem.