Re: [PATCH] drm/i915: Fix oopses in the overlay code due to i915_gem_active stuff

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Dec 07, 2016 at 05:56:47PM +0000, Chris Wilson wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> The i915_gem_active stuff doesn't like a NULL ->retire hook, but
> the overlay code can set it to NULL. That obviously ends up oopsing.
> Fix it by introducing a new helper to assign the retirement callback
> that will switch out the NULL function pointer with
> i915_gem_retire_noop.
> 
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Fixes: 0d9bdd886f29 ("drm/i915: Convert intel_overlay to request tracking")
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

lgtm, feel free to put yourself as the author is you want.

BTW I don't think we ever call the init_foo() thing on last_flip.
Should be do that in overlay_init() or some such place?

> ---
>  drivers/gpu/drm/i915/i915_gem_request.h | 19 +++++++++++++++++++
>  drivers/gpu/drm/i915/intel_overlay.c    |  3 ++-
>  2 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h
> index 2fc6b8b3f580..b0d50aa81acb 100644
> --- a/drivers/gpu/drm/i915/i915_gem_request.h
> +++ b/drivers/gpu/drm/i915/i915_gem_request.h
> @@ -440,6 +440,25 @@ i915_gem_active_set(struct i915_gem_active *active,
>  	rcu_assign_pointer(active->request, request);
>  }
>  
> +/**
> + * i915_gem_active_set_retire_fn - updates the retirement callback
> + * @active - the active tracker
> + * @fn - the routine called when the request is retired
> + * @mutex - struct_mutex used to guard retirements
> + *
> + * i915_gem_active_set_retire_fn() updates the function pointer that
> + * is called when the final request associated with the @active tracker
> + * is retired.
> + */
> +static inline void
> +i915_gem_active_set_retire_fn(struct i915_gem_active *active,
> +			      i915_gem_retire_fn fn,
> +			      struct mutex *mutex)
> +{
> +	lockdep_assert_held(mutex);
> +	active->retire = fn ?: i915_gem_retire_noop;
> +}
> +
>  static inline struct drm_i915_gem_request *
>  __i915_gem_active_peek(const struct i915_gem_active *active)
>  {
> diff --git a/drivers/gpu/drm/i915/intel_overlay.c b/drivers/gpu/drm/i915/intel_overlay.c
> index 354f8cec96bb..29509f3055c8 100644
> --- a/drivers/gpu/drm/i915/intel_overlay.c
> +++ b/drivers/gpu/drm/i915/intel_overlay.c
> @@ -216,7 +216,8 @@ static void intel_overlay_submit_request(struct intel_overlay *overlay,
>  {
>  	GEM_BUG_ON(i915_gem_active_peek(&overlay->last_flip,
>  					&overlay->i915->drm.struct_mutex));
> -	overlay->last_flip.retire = retire;
> +	i915_gem_active_set_retire_fn(&overlay->last_flip, retire,
> +				      &overlay->i915->drm.struct_mutex);
>  	i915_gem_active_set(&overlay->last_flip, req);
>  	i915_add_request(req);
>  }
> -- 
> 2.11.0

-- 
Ville Syrjälä
Intel OTC
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