[PATCH 16/21] drm/i915: Take object reference and trylock during eviction

[Maarten Lankhorst]

We want to add locking to i915_vma_unbind, but this requires a valid
object. Skip dead objects or busy objects from being evicted.

This unfortunately makes delayed destroyed objects unevictable,
but this will hopefully be fixed at a later date, when moving to ttm
style delayed destroy.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_shrinker.c | 14 +++-
 drivers/gpu/drm/i915/i915_gem_evict.c        | 67 ++++++++++++++++++--
 2 files changed, 73 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
index 7f7849b6296d..71e855fcbd8c 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
@@ -404,12 +404,22 @@ i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr
 	list_for_each_entry_safe(vma, next,
 				 &i915->ggtt.vm.bound_list, vm_link) {
 		unsigned long count = vma->node.size >> PAGE_SHIFT;
+		struct drm_i915_gem_object *obj;
 
 		if (!vma->iomap || i915_vma_is_active(vma))
 			continue;
 
-		if (__i915_vma_unbind(vma) == 0)
-			freed_pages += count;
+		obj = vma->obj;
+		if (!kref_get_unless_zero(&obj->base.refcount))
+			continue;
+
+		if (i915_gem_object_trylock(obj)) {
+			if (__i915_vma_unbind(vma) == 0)
+				freed_pages += count;
+
+			i915_gem_object_unlock(obj);
+		}
+		i915_gem_object_put(obj);
 	}
 	mutex_unlock(&i915->ggtt.vm.mutex);
 
diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c
index 2b73ddb11c66..a73345b80efe 100644
--- a/drivers/gpu/drm/i915/i915_gem_evict.c
+++ b/drivers/gpu/drm/i915/i915_gem_evict.c
@@ -58,6 +58,14 @@ mark_free(struct drm_mm_scan *scan,
 	if (i915_vma_is_pinned(vma))
 		return false;
 
+	if (!kref_get_unless_zero(&vma->obj->base.refcount))
+		return false;
+
+	if (!i915_gem_object_trylock(vma->obj)) {
+		i915_vma_put(vma);
+		return false;
+	}
+
 	list_add(&vma->evict_link, unwind);
 	return drm_mm_scan_add_block(scan, &vma->node);
 }
@@ -178,6 +186,8 @@ i915_gem_evict_something(struct i915_address_space *vm,
 	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
 		ret = drm_mm_scan_remove_block(&scan, &vma->node);
 		BUG_ON(ret);
+		i915_gem_object_unlock(vma->obj);
+		i915_gem_object_put(vma->obj);
 	}
 
 	/*
@@ -222,10 +232,13 @@ i915_gem_evict_something(struct i915_address_space *vm,
 	 * of any of our objects, thus corrupting the list).
 	 */
 	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
-		if (drm_mm_scan_remove_block(&scan, &vma->node))
+		if (drm_mm_scan_remove_block(&scan, &vma->node)) {
 			__i915_vma_pin(vma);
-		else
+		} else {
 			list_del(&vma->evict_link);
+			i915_gem_object_unlock(vma->obj);
+			i915_gem_object_put(vma->obj);
+		}
 	}
 
 	/* Unbinding will emit any required flushes */
@@ -234,16 +247,28 @@ i915_gem_evict_something(struct i915_address_space *vm,
 		__i915_vma_unpin(vma);
 		if (ret == 0)
 			ret = __i915_vma_unbind(vma);
+
+		i915_gem_object_unlock(vma->obj);
+		i915_gem_object_put(vma->obj);
 	}
 
 	while (ret == 0 && (node = drm_mm_scan_color_evict(&scan))) {
 		vma = container_of(node, struct i915_vma, node);
 
+
 		/* If we find any non-objects (!vma), we cannot evict them */
-		if (vma->node.color != I915_COLOR_UNEVICTABLE)
-			ret = __i915_vma_unbind(vma);
-		else
-			ret = -ENOSPC; /* XXX search failed, try again? */
+		if (vma->node.color != I915_COLOR_UNEVICTABLE &&
+		    !kref_get_unless_zero(&vma->obj->base.refcount)) {
+			struct drm_i915_gem_object *obj = vma->obj;
+
+			if (i915_gem_object_trylock(obj)) {
+				ret = __i915_vma_unbind(vma);
+				i915_gem_object_unlock(obj);
+			} else
+				ret = -ENOSPC;
+			i915_gem_object_put(obj);
+		} else
+			ret = -ENOSPC;
 	}
 
 	return ret;
@@ -333,6 +358,17 @@ int i915_gem_evict_for_node(struct i915_address_space *vm,
 			break;
 		}
 
+		if (!kref_get_unless_zero(&vma->obj->base.refcount)) {
+			ret = -ENOSPC;
+			break;
+		}
+
+		if (!i915_gem_object_trylock(vma->obj)) {
+			ret = -ENOSPC;
+			i915_gem_object_put(vma->obj);
+			break;
+		}
+
 		/*
 		 * Never show fear in the face of dragons!
 		 *
@@ -347,9 +383,14 @@ int i915_gem_evict_for_node(struct i915_address_space *vm,
 	}
 
 	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
+		struct drm_i915_gem_object *obj = vma->obj;
+
 		__i915_vma_unpin(vma);
 		if (ret == 0)
 			ret = __i915_vma_unbind(vma);
+
+		i915_gem_object_unlock(obj);
+		i915_gem_object_put(obj);
 	}
 
 	return ret;
@@ -393,6 +434,14 @@ int i915_gem_evict_vm(struct i915_address_space *vm)
 			if (i915_vma_is_pinned(vma))
 				continue;
 
+			if (!kref_get_unless_zero(&vma->obj->base.refcount))
+				continue;
+
+			if (!i915_gem_object_trylock(vma->obj)) {
+				i915_gem_object_put(vma->obj);
+				continue;
+			}
+
 			__i915_vma_pin(vma);
 			list_add(&vma->evict_link, &eviction_list);
 		}
@@ -401,11 +450,17 @@ int i915_gem_evict_vm(struct i915_address_space *vm)
 
 		ret = 0;
 		list_for_each_entry_safe(vma, vn, &eviction_list, evict_link) {
+			struct drm_i915_gem_object *obj = vma->obj;
+
 			__i915_vma_unpin(vma);
+
 			if (ret == 0)
 				ret = __i915_vma_unbind(vma);
 			if (ret != -EINTR) /* "Get me out of here!" */
 				ret = 0;
+
+			i915_gem_object_unlock(obj);
+			i915_gem_object_put(obj);
 		}
 	} while (ret == 0);
 
-- 
2.33.0