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Commit ae3db24a authored by Daniel Vetter's avatar Daniel Vetter Committed by Eric Anholt
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drm/i915: extract fence stealing code 



The spaghetti logic in there tripped up my brain's code parser for a
few secs. Prevent this from happening again by extracting the fence
stealing code into a seperate functions. IMHO this slightly clears up
the code flow.

v2: Beautified according to ickle's comments.
v3: ickle forgot to flush his comment queue ... Now there's also a
we-are-paranoid BUG_ON in there.
v4: I've forgotten to switch on my brain when doing v3. Now the BUG_ON
actually checks something useful.
v5: Clean up a stale comment as noted by Eric Anholt.

Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: default avatarEric Anholt <eric@anholt.net>
parent 4a87b8ca

drivers/gpu/drm/i915/i915_gem.c

+60 −47
Original line number Diff line number Diff line
@@ -2382,6 +2382,58 @@ static void i830_write_fence_reg(struct drm_i915_fence_reg *reg) 
	I915_WRITE(FENCE_REG_830_0 + (regnum * 4), val);

}



static int i915_find_fence_reg(struct drm_device *dev)

{

	struct drm_i915_fence_reg *reg = NULL;

	struct drm_i915_gem_object *obj_priv = NULL;

	struct drm_i915_private *dev_priv = dev->dev_private;

	struct drm_gem_object *obj = NULL;

	int i, avail, ret;



	/* First try to find a free reg */

	avail = 0;

	for (i = dev_priv->fence_reg_start; i < dev_priv->num_fence_regs; i++) {

		reg = &dev_priv->fence_regs[i];

		if (!reg->obj)

			return i;



		obj_priv = reg->obj->driver_private;

		if (!obj_priv->pin_count)

		    avail++;

	}



	if (avail == 0)

		return -ENOSPC;



	/* None available, try to steal one or wait for a user to finish */

	i = I915_FENCE_REG_NONE;

	list_for_each_entry(obj_priv, &dev_priv->mm.fence_list,

			    fence_list) {

		obj = obj_priv->obj;



		if (obj_priv->pin_count)

			continue;



		/* found one! */

		i = obj_priv->fence_reg;

		break;

	}



	BUG_ON(i == I915_FENCE_REG_NONE);



	/* We only have a reference on obj from the active list. put_fence_reg

	 * might drop that one, causing a use-after-free in it. So hold a

	 * private reference to obj like the other callers of put_fence_reg

	 * (set_tiling ioctl) do. */

	drm_gem_object_reference(obj);

	ret = i915_gem_object_put_fence_reg(obj);

	drm_gem_object_unreference(obj);

	if (ret != 0)

		return ret;



	return i;

}



/**

 * i915_gem_object_get_fence_reg - set up a fence reg for an object

 * @obj: object to map through a fence reg
@@ -2402,8 +2454,7 @@ i915_gem_object_get_fence_reg(struct drm_gem_object *obj) 
	struct drm_i915_private *dev_priv = dev->dev_private;

	struct drm_i915_gem_object *obj_priv = obj->driver_private;

	struct drm_i915_fence_reg *reg = NULL;

	struct drm_i915_gem_object *old_obj_priv = NULL;

	int i, ret, avail;

	int ret;



	/* Just update our place in the LRU if our fence is getting used. */

	if (obj_priv->fence_reg != I915_FENCE_REG_NONE) {
@@ -2431,51 +2482,12 @@ i915_gem_object_get_fence_reg(struct drm_gem_object *obj) 
		break;

	}



	/* First try to find a free reg */

	avail = 0;

	for (i = dev_priv->fence_reg_start; i < dev_priv->num_fence_regs; i++) {

		reg = &dev_priv->fence_regs[i];

		if (!reg->obj)

			break;



		old_obj_priv = reg->obj->driver_private;

		if (!old_obj_priv->pin_count)

		    avail++;

	}



	/* None available, try to steal one or wait for a user to finish */

	if (i == dev_priv->num_fence_regs) {

		struct drm_gem_object *old_obj = NULL;



		if (avail == 0)

			return -ENOSPC;



		list_for_each_entry(old_obj_priv, &dev_priv->mm.fence_list,

				    fence_list) {

			old_obj = old_obj_priv->obj;



			if (old_obj_priv->pin_count)

				continue;



			/* Take a reference, as otherwise the wait_rendering

			 * below may cause the object to get freed out from

			 * under us.

			 */

			drm_gem_object_reference(old_obj);



			break;

		}



		i = old_obj_priv->fence_reg;

		reg = &dev_priv->fence_regs[i];



		ret = i915_gem_object_put_fence_reg(old_obj);

		drm_gem_object_unreference(old_obj);

		if (ret != 0) 

	ret = i915_find_fence_reg(dev);

	if (ret < 0)

		return ret;

	}



	obj_priv->fence_reg = i;

	obj_priv->fence_reg = ret;

	reg = &dev_priv->fence_regs[obj_priv->fence_reg];

	list_add_tail(&obj_priv->fence_list, &dev_priv->mm.fence_list);



	reg->obj = obj;
@@ -2489,7 +2501,8 @@ i915_gem_object_get_fence_reg(struct drm_gem_object *obj) 
	else

		i830_write_fence_reg(reg);



	trace_i915_gem_object_get_fence(obj, i, obj_priv->tiling_mode);

	trace_i915_gem_object_get_fence(obj, obj_priv->fence_reg,

			obj_priv->tiling_mode);



	return 0;

}