drm/i915: Move object close under its own lock

Use i915_gem_object_lock() to guard the LUT and active reference to
allow us to break free of struct_mutex for handling GEM_CLOSE.

Testcase: igt/gem_close_race
Testcase: igt/gem_exec_parallel
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190606112320.9704-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gem/i915_gem_context.c

@@ -95,24 +95,45 @@ void i915_lut_handle_free(struct i915_lut_handle *lut)
 
 static void lut_close(struct i915_gem_context *ctx)
 {
-	struct i915_lut_handle *lut, *ln;
 	struct radix_tree_iter iter;
 	void __rcu **slot;
 
-	list_for_each_entry_safe(lut, ln, &ctx->handles_list, ctx_link) {
-		list_del(&lut->obj_link);
-		i915_lut_handle_free(lut);
-	}
-	INIT_LIST_HEAD(&ctx->handles_list);
+	lockdep_assert_held(&ctx->mutex);
 
 	rcu_read_lock();
 	radix_tree_for_each_slot(slot, &ctx->handles_vma, &iter, 0) {
 		struct i915_vma *vma = rcu_dereference_raw(*slot);
+		struct drm_i915_gem_object *obj = vma->obj;
+		struct i915_lut_handle *lut;
+
+		if (!kref_get_unless_zero(&obj->base.refcount))
+			continue;
 
-		radix_tree_iter_delete(&ctx->handles_vma, &iter, slot);
+		rcu_read_unlock();
+		i915_gem_object_lock(obj);
+		list_for_each_entry(lut, &obj->lut_list, obj_link) {
+			if (lut->ctx != ctx)
+				continue;
 
-		vma->open_count--;
-		i915_vma_put(vma);
+			if (lut->handle != iter.index)
+				continue;
+
+			list_del(&lut->obj_link);
+			break;
+		}
+		i915_gem_object_unlock(obj);
+		rcu_read_lock();
+
+		if (&lut->obj_link != &obj->lut_list) {
+			i915_lut_handle_free(lut);
+			radix_tree_iter_delete(&ctx->handles_vma, &iter, slot);
+			if (atomic_dec_and_test(&vma->open_count) &&
+			    !i915_vma_is_ggtt(vma))
+				i915_vma_close(vma);
+			i915_gem_object_put(obj);
+		}
+
+		i915_gem_object_put(obj);
 	}
 	rcu_read_unlock();
 }
@@ -250,15 +271,9 @@ static void free_engines(struct i915_gem_engines *e)
 	__free_engines(e, e->num_engines);
 }
 
-static void free_engines_rcu(struct work_struct *wrk)
+static void free_engines_rcu(struct rcu_head *rcu)
 {
-	struct i915_gem_engines *e =
-		container_of(wrk, struct i915_gem_engines, rcu.work);
-	struct drm_i915_private *i915 = e->i915;
-
-	mutex_lock(&i915->drm.struct_mutex);
-	free_engines(e);
-	mutex_unlock(&i915->drm.struct_mutex);
+	free_engines(container_of(rcu, struct i915_gem_engines, rcu));
 }
 
 static struct i915_gem_engines *default_engines(struct i915_gem_context *ctx)
@@ -271,7 +286,7 @@ static struct i915_gem_engines *default_engines(struct i915_gem_context *ctx)
 	if (!e)
 		return ERR_PTR(-ENOMEM);
 
-	e->i915 = ctx->i915;
+	init_rcu_head(&e->rcu);
 	for_each_engine(engine, ctx->i915, id) {
 		struct intel_context *ce;
 
@@ -359,7 +374,10 @@ void i915_gem_context_release(struct kref *ref)
 
 static void context_close(struct i915_gem_context *ctx)
 {
+	mutex_lock(&ctx->mutex);
+
 	i915_gem_context_set_closed(ctx);
+	ctx->file_priv = ERR_PTR(-EBADF);
 
 	/*
 	 * This context will never again be assinged to HW, so we can
@@ -374,7 +392,7 @@ static void context_close(struct i915_gem_context *ctx)
 	 */
 	lut_close(ctx);
 
-	ctx->file_priv = ERR_PTR(-EBADF);
+	mutex_unlock(&ctx->mutex);
 	i915_gem_context_put(ctx);
 }
 
@@ -429,7 +447,6 @@ __create_context(struct drm_i915_private *dev_priv)
 	RCU_INIT_POINTER(ctx->engines, e);
 
 	INIT_RADIX_TREE(&ctx->handles_vma, GFP_KERNEL);
-	INIT_LIST_HEAD(&ctx->handles_list);
 	INIT_LIST_HEAD(&ctx->hw_id_link);
 
 	/* NB: Mark all slices as needing a remap so that when the context first
@@ -772,9 +789,7 @@ int i915_gem_context_open(struct drm_i915_private *i915,
 	return 0;
 
 err_ctx:
-	mutex_lock(&i915->drm.struct_mutex);
 	context_close(ctx);
-	mutex_unlock(&i915->drm.struct_mutex);
 err:
 	idr_destroy(&file_priv->vm_idr);
 	idr_destroy(&file_priv->context_idr);
@@ -787,8 +802,6 @@ void i915_gem_context_close(struct drm_file *file)
 {
 	struct drm_i915_file_private *file_priv = file->driver_priv;
 
-	lockdep_assert_held(&file_priv->dev_priv->drm.struct_mutex);
-
 	idr_for_each(&file_priv->context_idr, context_idr_cleanup, NULL);
 	idr_destroy(&file_priv->context_idr);
 	mutex_destroy(&file_priv->context_idr_lock);
@@ -1093,7 +1106,9 @@ static int set_ppgtt(struct drm_i915_file_private *file_priv,
 		goto unlock;
 
 	/* Teardown the existing obj:vma cache, it will have to be rebuilt. */
+	mutex_lock(&ctx->mutex);
 	lut_close(ctx);
+	mutex_unlock(&ctx->mutex);
 
 	old = __set_ppgtt(ctx, ppgtt);
 
@@ -1612,7 +1627,7 @@ set_engines(struct i915_gem_context *ctx,
 	if (!set.engines)
 		return -ENOMEM;
 
-	set.engines->i915 = ctx->i915;
+	init_rcu_head(&set.engines->rcu);
 	for (n = 0; n < num_engines; n++) {
 		struct i915_engine_class_instance ci;
 		struct intel_engine_cs *engine;
@@ -1666,8 +1681,7 @@ set_engines(struct i915_gem_context *ctx,
 	rcu_swap_protected(ctx->engines, set.engines, 1);
 	mutex_unlock(&ctx->engines_mutex);
 
-	INIT_RCU_WORK(&set.engines->rcu, free_engines_rcu);
-	queue_rcu_work(system_wq, &set.engines->rcu);
+	call_rcu(&set.engines->rcu, free_engines_rcu);
 
 	return 0;
 }
@@ -1682,7 +1696,7 @@ __copy_engines(struct i915_gem_engines *e)
 	if (!copy)
 		return ERR_PTR(-ENOMEM);
 
-	copy->i915 = e->i915;
+	init_rcu_head(&copy->rcu);
 	for (n = 0; n < e->num_engines; n++) {
 		if (e->engines[n])
 			copy->engines[n] = intel_context_get(e->engines[n]);
@@ -1769,8 +1783,7 @@ get_engines(struct i915_gem_context *ctx,
 	args->size = size;
 
 err_free:
-	INIT_RCU_WORK(&e->rcu, free_engines_rcu);
-	queue_rcu_work(system_wq, &e->rcu);
+	free_engines(e);
 	return err;
 }
 
@@ -1891,7 +1904,7 @@ static int clone_engines(struct i915_gem_context *dst,
 	if (!clone)
 		goto err_unlock;
 
-	clone->i915 = dst->i915;
+	init_rcu_head(&clone->rcu);
 	for (n = 0; n < e->num_engines; n++) {
 		struct intel_engine_cs *engine;
 
@@ -2163,9 +2176,7 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
 	return 0;
 
 err_ctx:
-	mutex_lock(&dev->struct_mutex);
 	context_close(ext_data.ctx);
-	mutex_unlock(&dev->struct_mutex);
 	return ret;
 }
 
@@ -2190,10 +2201,7 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
 	if (!ctx)
 		return -ENOENT;
 
-	mutex_lock(&dev->struct_mutex);
 	context_close(ctx);
-	mutex_unlock(&dev->struct_mutex);
-
 	return 0;
 }
 

drivers/gpu/drm/i915/gem/i915_gem_context_types.h

@@ -30,8 +30,7 @@ struct i915_timeline;
 struct intel_ring;
 
 struct i915_gem_engines {
-	struct rcu_work rcu;
-	struct drm_i915_private *i915;
+	struct rcu_head rcu;
 	unsigned int num_engines;
 	struct intel_context *engines[];
 };
@@ -192,17 +191,12 @@ struct i915_gem_context {
 	/** remap_slice: Bitmask of cache lines that need remapping */
 	u8 remap_slice;
 
-	/** handles_vma: rbtree to look up our context specific obj/vma for
+	/**
+	 * handles_vma: rbtree to look up our context specific obj/vma for
 	 * the user handle. (user handles are per fd, but the binding is
 	 * per vm, which may be one per context or shared with the global GTT)
 	 */
 	struct radix_tree_root handles_vma;
-
-	/** handles_list: reverse list of all the rbtree entries in use for
-	 * this context, which allows us to free all the allocations on
-	 * context close.
-	 */
-	struct list_head handles_list;
 };
 
 #endif /* __I915_GEM_CONTEXT_TYPES_H__ */

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

@@ -801,9 +801,6 @@ static int eb_lookup_vmas(struct i915_execbuffer *eb)
 	unsigned int i, batch;
 	int err;
 
-	if (unlikely(i915_gem_context_is_closed(eb->gem_context)))
-		return -ENOENT;
-
 	if (unlikely(i915_gem_context_is_banned(eb->gem_context)))
 		return -EIO;
 
@@ -812,6 +809,12 @@ static int eb_lookup_vmas(struct i915_execbuffer *eb)
 
 	batch = eb_batch_index(eb);
 
+	mutex_lock(&eb->gem_context->mutex);
+	if (unlikely(i915_gem_context_is_closed(eb->gem_context))) {
+		err = -ENOENT;
+		goto err_ctx;
+	}
+
 	for (i = 0; i < eb->buffer_count; i++) {
 		u32 handle = eb->exec[i].handle;
 		struct i915_lut_handle *lut;
@@ -845,13 +848,15 @@ static int eb_lookup_vmas(struct i915_execbuffer *eb)
 			goto err_obj;
 		}
 
-		/* transfer ref to ctx */
-		if (!vma->open_count++)
+		/* transfer ref to lut */
+		if (!atomic_fetch_inc(&vma->open_count))
 			i915_vma_reopen(vma);
-		list_add(&lut->obj_link, &obj->lut_list);
-		list_add(&lut->ctx_link, &eb->gem_context->handles_list);
-		lut->ctx = eb->gem_context;
 		lut->handle = handle;
+		lut->ctx = eb->gem_context;
+
+		i915_gem_object_lock(obj);
+		list_add(&lut->obj_link, &obj->lut_list);
+		i915_gem_object_unlock(obj);
 
 add_vma:
 		err = eb_add_vma(eb, i, batch, vma);
@@ -864,13 +869,17 @@ static int eb_lookup_vmas(struct i915_execbuffer *eb)
 			   eb_vma_misplaced(&eb->exec[i], vma, eb->flags[i]));
 	}
 
+	mutex_unlock(&eb->gem_context->mutex);
+
 	eb->args->flags |= __EXEC_VALIDATED;
 	return eb_reserve(eb);
 
 err_obj:
 	i915_gem_object_put(obj);
 err_vma:
 	eb->vma[i] = NULL;
+err_ctx:
+	mutex_unlock(&eb->gem_context->mutex);
 	return err;
 }
 

drivers/gpu/drm/i915/gem/i915_gem_object.c

@@ -105,39 +105,47 @@ void i915_gem_object_set_cache_coherency(struct drm_i915_gem_object *obj,
 
 void i915_gem_close_object(struct drm_gem_object *gem, struct drm_file *file)
 {
-	struct drm_i915_private *i915 = to_i915(gem->dev);
 	struct drm_i915_gem_object *obj = to_intel_bo(gem);
 	struct drm_i915_file_private *fpriv = file->driver_priv;
 	struct i915_lut_handle *lut, *ln;
+	LIST_HEAD(close);
 
-	mutex_lock(&i915->drm.struct_mutex);
-
+	i915_gem_object_lock(obj);
 	list_for_each_entry_safe(lut, ln, &obj->lut_list, obj_link) {
 		struct i915_gem_context *ctx = lut->ctx;
-		struct i915_vma *vma;
 
-		GEM_BUG_ON(ctx->file_priv == ERR_PTR(-EBADF));
 		if (ctx->file_priv != fpriv)
 			continue;
 
-		vma = radix_tree_delete(&ctx->handles_vma, lut->handle);
-		GEM_BUG_ON(vma->obj != obj);
+		i915_gem_context_get(ctx);
+		list_move(&lut->obj_link, &close);
+	}
+	i915_gem_object_unlock(obj);
 
-		/* We allow the process to have multiple handles to the same
+	list_for_each_entry_safe(lut, ln, &close, obj_link) {
+		struct i915_gem_context *ctx = lut->ctx;
+		struct i915_vma *vma;
+
+		/*
+		 * We allow the process to have multiple handles to the same
 		 * vma, in the same fd namespace, by virtue of flink/open.
 		 */
-		GEM_BUG_ON(!vma->open_count);
-		if (!--vma->open_count && !i915_vma_is_ggtt(vma))
-			i915_vma_close(vma);
 
-		list_del(&lut->obj_link);
-		list_del(&lut->ctx_link);
+		mutex_lock(&ctx->mutex);
+		vma = radix_tree_delete(&ctx->handles_vma, lut->handle);
+		if (vma) {
+			GEM_BUG_ON(vma->obj != obj);
+			GEM_BUG_ON(!atomic_read(&vma->open_count));
+			if (atomic_dec_and_test(&vma->open_count) &&
+			    !i915_vma_is_ggtt(vma))
+				i915_vma_close(vma);
+		}
+		mutex_unlock(&ctx->mutex);
 
+		i915_gem_context_put(lut->ctx);
 		i915_lut_handle_free(lut);
 		i915_gem_object_put(obj);
 	}
-
-	mutex_unlock(&i915->drm.struct_mutex);
 }
 
 static bool discard_backing_storage(struct drm_i915_gem_object *obj)

drivers/gpu/drm/i915/gem/i915_gem_object_types.h

@@ -24,7 +24,6 @@ struct drm_i915_gem_object;
  */
 struct i915_lut_handle {
 	struct list_head obj_link;
-	struct list_head ctx_link;
 	struct i915_gem_context *ctx;
 	u32 handle;
 };

drivers/gpu/drm/i915/gem/selftests/mock_context.c

@@ -30,7 +30,6 @@ mock_context(struct drm_i915_private *i915,
 	RCU_INIT_POINTER(ctx->engines, e);
 
 	INIT_RADIX_TREE(&ctx->handles_vma, GFP_KERNEL);
-	INIT_LIST_HEAD(&ctx->handles_list);
 	INIT_LIST_HEAD(&ctx->hw_id_link);
 	mutex_init(&ctx->mutex);
 

drivers/gpu/drm/i915/i915_drv.h

@@ -1899,10 +1899,12 @@ struct drm_i915_private {
 		} timelines;
 
 		struct list_head active_rings;
-		struct list_head closed_vma;
 
 		struct intel_wakeref wakeref;
 
+		struct list_head closed_vma;
+		spinlock_t closed_lock; /* guards the list of closed_vma */
+
 		/**
 		 * Is the GPU currently considered idle, or busy executing
 		 * userspace requests? Whilst idle, we allow runtime power

drivers/gpu/drm/i915/i915_gem.c

@@ -1784,6 +1784,7 @@ int i915_gem_init_early(struct drm_i915_private *dev_priv)
 
 	INIT_LIST_HEAD(&dev_priv->gt.active_rings);
 	INIT_LIST_HEAD(&dev_priv->gt.closed_vma);
+	spin_lock_init(&dev_priv->gt.closed_lock);
 
 	i915_gem_init__mm(dev_priv);
 	i915_gem_init__pm(dev_priv);