[Intel-gfx] [PATCH] drm/i915: Handle recursive shrinker for vma->last_active allocation

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-07-19 12:18:26)
> 
> On 19/07/2018 08:22, Chris Wilson wrote:
> > If we call into the shrinker for direct relcaim inside kmalloc, it will
> > retire the requests. If we retire the vma->last_active while a new
> > i915_vma_move_to_active() we can upset the delicate bookkeeping required
> > for the cache. After the possible invocation of the shrinker, we need to
> > double check the vma->last_active is still valid.
> > 
> > Fixes: 8b293eb53a7d ("drm/i915: Track the last-active inside the i915_vma")
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > ---
> >   drivers/gpu/drm/i915/i915_vma.c | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> > index ed4e0fb558f7..11d834f94220 100644
> > --- a/drivers/gpu/drm/i915/i915_vma.c
> > +++ b/drivers/gpu/drm/i915/i915_vma.c
> > @@ -942,6 +942,14 @@ static struct i915_gem_active *active_instance(struct i915_vma *vma, u64 idx)
> >       }
> >   
> >       active = kmalloc(sizeof(*active), GFP_KERNEL);
> > +
> > +     /* kmalloc may retire the vma->last_active request (thanks shrinker)! */
> > +     if (unlikely(!i915_gem_active_raw(&vma->last_active,
> > +                                       &vma->vm->i915->drm.struct_mutex))) {
> > +             kfree(active);
> > +             goto out;
> > +     }
> > +
> >       if (unlikely(!active))
> >               return ERR_PTR(-ENOMEM);
> >   
> > 
> 
> Fun!
> 
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Pushed to keep CI ticking over.
-Chris