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

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

On 03/10/2015 12:19 PM, Chris Wilson wrote:
> On Tue, Mar 10, 2015 at 12:02:28PM +0000, Tvrtko Ursulin wrote:
>>> @@ -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?
>
> It's a dummy mutex that only exists to keep the WARNs quiet. This phase
> of initialisation is explicitly single-threaded.

Would it be a simpler fix then to move the mutex only around 
pin_and_fence_fb_obj?

Regards,

Tvrtko
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