On Thu, Jun 04, 2020 at 12:36:23PM -0700, jorhand@xxxxxxxxxxxxxxxxxxx wrote:
> From: Jordan Hand <jorhand@xxxxxxxxxxxxxxxxxxx>
>
> If a child swnode is unregistered after it's parent, it can lead to
> undefined behavior.
Crashing the system is not really "undefined" :)
> When a swnode is unregistered, recursively free it's children to avoid
> this condition.
Are you sure? Why would you be unregistering a child after it's parent?
Why not just do not do that?
>
> Signed-off-by: Jordan Hand <jorhand@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/base/swnode.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
> index e5eb27375416..e63093b1542b 100644
> --- a/drivers/base/swnode.c
> +++ b/drivers/base/swnode.c
> @@ -619,6 +619,8 @@ static void software_node_release(struct kobject *kobj)
> property_entries_free(swnode->node->properties);
> kfree(swnode->node);
> }
> +
> + list_del(&kobj->entry);
> ida_destroy(&swnode->child_ids);
> kfree(swnode);
> }
> @@ -712,11 +714,6 @@ EXPORT_SYMBOL_GPL(software_node_register_nodes);
> * @nodes: Zero terminated array of software nodes to be unregistered
> *
> * Unregister multiple software nodes at once.
> - *
> - * NOTE: Be careful using this call if the nodes had parent pointers set up in
> - * them before registering. If so, it is wiser to remove the nodes
> - * individually, in the correct order (child before parent) instead of relying
> - * on the sequential order of the list of nodes in the array.
> */
> void software_node_unregister_nodes(const struct software_node *nodes)
> {
> @@ -839,10 +836,16 @@ EXPORT_SYMBOL_GPL(fwnode_create_software_node);
> void fwnode_remove_software_node(struct fwnode_handle *fwnode)
> {
> struct swnode *swnode = to_swnode(fwnode);
> + struct swnode *child = NULL;
>
> if (!swnode)
> return;
>
> + while (!list_empty(&swnode->children)) {
> + child = list_first_entry_or_null(&swnode->children, struct swnode, entry);
> + fwnode_remove_software_node(&child->fwnode);
You should document that you just changed the behaivor here, as you are
now really doing fwnode_remove_software_node_and_all_children().
but again, why? Who wants to unregister a child before a parent?
thanks,
greg k-h
