Re: 5.3-rc3: Frozen graphics with kcompactd migrating i915 pages

[Linus Torvalds]

On Thu, Sep 12, 2019 at 12:51 PM Martin Wilck <Martin.Wilck@xxxxxxxx> wrote:
>
> Is there an alternative to reverting aa56a292ce62 ("drm/i915/userptr:
> Acquire the page lock around set_page_dirty()")? And if we do, what
> would be the consequences? Would other patches need to be reverted,
> too?

Looking at that commit, and the backtrace of the lockup, I think that
reverting it is the correct thing to do.

You can't take the page lock in invalidate_range(), since it's called
from try_to_unmap(), which is called with the page lock already held.

So commit aa56a292ce62 is just fundamentally completely wrong and
should be reverted.

               Linus