Re: [PATCH 2/2] drm/i915: Move drm_framebuffer_unreference out of struct_mutex for takeover

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

Hi,

On 02/16/2015 02:31 PM, Chris Wilson wrote:
> intel_user_framebuffer_destroy() requires the struct_mutex for its
> object bookkeeping, so this means that all calls to
> drm_framebuffer_reference must be held without that lock.

Same comment on the commit message as 1/2.

> References: https://bugs.freedesktop.org/show_bug.cgi?id=89166
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/intel_display.c | 13 ++++++++++---
>   1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 6e1da7da5cca..aba36662d511 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -13672,6 +13672,8 @@ void intel_modeset_gem_init(struct drm_device *dev)
>   	struct drm_i915_private *dev_priv = dev->dev_private;
>   	struct drm_crtc *c;
>   	struct drm_i915_gem_object *obj;
> +	struct drm_plane *unused[I915_MAX_PIPES];
> +	int n_unused = 0;
>
>   	mutex_lock(&dev->struct_mutex);
>   	intel_init_gt_powersave(dev);
> @@ -13707,13 +13709,18 @@ void intel_modeset_gem_init(struct drm_device *dev)
>   					       NULL)) {
>   			DRM_ERROR("failed to pin boot fb on pipe %d\n",
>   				  to_intel_crtc(c)->pipe);
> -			drm_framebuffer_unreference(c->primary->fb);
> -			c->primary->fb = NULL;
> -			update_state_fb(c->primary);
> +			unused[n_unused++] = c->primary;
>   		}
>   	}
>   	mutex_unlock(&dev->struct_mutex);
>
> +	while (n_unused--) {
> +		struct drm_plane *p = unused[n_unused];
> +		drm_framebuffer_unreference(p->fb);
> +		p->fb = NULL;
> +		update_state_fb(p);
> +	}
> +

For this one I am not sure. Should c->primary->fb = NULL remain under 
the locked loop? If not what is the the mutex protecting then?

Regards,

Tvrtko

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