Re: [PATCH] drm/i915: Migrate stolen objects before hibernation

From: Chris Wilson <chris@chris-wilson.co.uk>
To: intel-gfx@lists.freedesktop.org
Cc: Imre Deak <imre.deak@linux.intel.com>, Akash Goel <akash.goel@intel.com>
Subject: Re: [PATCH] drm/i915: Migrate stolen objects before hibernation
Date: Tue, 30 Jun 2015 11:31:38 +0100	[thread overview]
Message-ID: <20150630103138.GF1381@nuc-i3427.alporthouse.com> (raw)
In-Reply-To: <1435658288-31656-1-git-send-email-chris@chris-wilson.co.uk>

On Tue, Jun 30, 2015 at 10:58:08AM +0100, Chris Wilson wrote:
> +int
> +i915_gem_freeze(struct drm_device *dev)
> +{
> +	/* Called before freeze when hibernating */
> +	struct drm_i915_private *i915 = to_i915(dev);
> +	struct drm_i915_gem_object *obj, *tmp;
> +	int ret;
> +
> +	/* Across hibernation, the stolen area is not preserved.
> +	 * Anything inside stolen must copied back to normal
> +	 * memory if we wish to preserve it.
> +	 */

And I forgot to add the double pass + reference/unreference dance here

> +	list_for_each_entry_safe(obj, tmp, &i915->mm.stolen_list, stolen_link) {
> +		if (obj->madv != I915_MADV_WILLNEED) {
> +			/* XXX any point in setting this? The objects for which
> +			 * we preserve never unset it afterwards.
> +			 */
> +			obj->madv = __I915_MADV_PURGED;
> +			continue;
> +		}
> +
> +		ret = i915_gem_object_migrate_stolen_to_shmemfs(obj);
> +		if (ret)
> +			return ret;
> +	}

should be

+	INIT_LIST_HEAD(&migrate);
+       list_for_each_entry_safe(obj, tmp, &i915->mm.stolen_list, stolen_link) {
+               if (obj->madv != I915_MADV_WILLNEED)
+                       continue;
+
+               /* In the general case, this object may only be alive due to
+                * an active reference, and that may disappear when we unbind
+                * any of the objects (and so wait upon the GPU and retire
+                * requests). To prevent one of the objects from disappearing
+                * beneath us, we need to take a reference to each as we
+                * build the migration list.
+                *
+                * This is similar to the strategy required whilst shrinking
+                * or evicting objects (for the same reason).
+                */
+               drm_gem_object_reference(&obj->base);
+               list_move(&obj->stolen_link, &migrate);
+       }
+
+       ret = 0;
+       list_for_each_entry_safe(obj, tmp, &migrate, stolen_link) {
+               if (ret == 0)
+                       ret = i915_gem_object_migrate_stolen_to_shmemfs(obj);
+               drm_gem_object_unreference(&obj->base);
+       }
+       list_splice(&migrate, &i915->mm.stolen_list);
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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