[Intel-gfx] [PATCH] drm/i915: Kick rcu harder to free objects

[Ville Syrjälä]

On Thu, Sep 08, 2022 at 04:32:56PM +0200, Das, Nirmoy wrote:
> Hi Ville,
> 
> 
> I fixed a similar issue in DII but I couldn't reproduce it in drm
> 
> http://intel-gfx-pw.fi.intel.com/patch/228850/?series=15910&rev=2.
> 
> I wonder if that fixes the problem you are facing then I can send that 
> to drm.

CI can tell you. It has been complaining about this for ages without
anyone doing anything about it.

> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c 
> b/drivers/gpu/drm/i915/i915_gem.c
> index 7809be3a6840..5438e9277924 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1213,7 +1213,7 @@  void i915_gem_init_early(struct drm_i915_private 
> *dev_priv)
> 
>   void i915_gem_cleanup_early(struct drm_i915_private *dev_priv)
>   {
> -    i915_gem_drain_freed_objects(dev_priv);
> +    i915_gem_drain_workqueue(dev_priv);
>       GEM_BUG_ON(!llist_empty(&dev_priv->mm.free_list));
>       GEM_BUG_ON(atomic_read(&dev_priv->mm.free_count));
>       drm_WARN_ON(&dev_priv->drm, dev_priv->mm.shrink_count);
> 
> 
> Regards,
> 
> Nirmoy
> 
> On 9/6/2022 7:46 PM, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> >
> > On gen3 the selftests are pretty much always tripping this:
> > <4> [383.822424] pci 0000:00:02.0: drm_WARN_ON(dev_priv->mm.shrink_count)
> > <4> [383.822546] WARNING: CPU: 2 PID: 3560 at drivers/gpu/drm/i915/i915_gem.c:1223 i915_gem_cleanup_early+0x96/0xb0 [i915]
> >
> > Looks to be due to the status page object lingering on the
> > purge_list. Call synchronize_rcu() ahead of it to make more
> > sure all objects have been freed.
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >   drivers/gpu/drm/i915/i915_gem.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index 0f49ec9d494a..5b61f7ad6473 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -1098,6 +1098,7 @@ void i915_gem_drain_freed_objects(struct drm_i915_private *i915)
> >   		flush_delayed_work(&i915->bdev.wq);
> >   		rcu_barrier();
> >   	}
> > +	synchronize_rcu();
> >   }
> >   
> >   /*

-- 
Ville Syrjälä
Intel