[Intel-gfx] [PATCH 3/3] drm/i915/userptr: Probe vma range before gup

[Chris Wilson]

Quoting Tvrtko Ursulin (2019-01-15 10:27:02)
> 
> On 14/01/2019 21:17, Chris Wilson wrote:
> > +     if (err)
> > +             goto err_unlock;
> > +
> > +     err = __i915_gem_userptr_get_pages_schedule(obj);
> > +     if (err == -EAGAIN)
> >               __i915_gem_userptr_set_active(obj, true);
> >   
> > -     if (IS_ERR(pages))
> > -             release_pages(pvec, pinned);
> > -     kvfree(pvec);
> > +err_unlock:
> > +     up_read(&mm->mmap_sem);
> 
> May be safer to drop the lock earlier, immediately after probe. I don't 
> see holding it while queuing the worker and doing internal book-keeping 
> is useful and might just create more lock chain dependencies.

Hmm, I thought we need to cover up to set-active (probe + queue + insert
into rbtree) as I thought the mmu-invalidate was under the mmap_sem wlock.
-Chris