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

[Das, Nirmoy]

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.

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();
>   }
>   
>   /*