On Sat, Jun 23, 2018 at 11:08:51AM +0200, Jouke Witteveen wrote:
> As unregistering a hook takes it off the hook list, we should use a safe
> for_each loop when we potentially unregister a hook.
> 
> Signed-off-by: Jouke Witteveen <j.wittev...@gmail.com>
> ---

I would like to draw attention to this patch. It fixes a very noticable
regression for owners of Thinkpad 13 laptops. The thinkpad_acpi driver
currently does not support that line of laptops [1]. As a result, users
cannot boot the 4.17 kernel on those machines.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=200333#c1

>  drivers/acpi/battery.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
> index b0113a58..d79ad844 100644
> --- a/drivers/acpi/battery.c
> +++ b/drivers/acpi/battery.c
> @@ -717,10 +717,11 @@ void battery_hook_register(struct acpi_battery_hook 
> *hook)
>                        */
>                       pr_err("extension failed to load: %s", hook->name);
>                       __battery_hook_unregister(hook, 0);
> -                     return;
> +                     goto end;
>               }
>       }
>       pr_info("new extension: %s\n", hook->name);
> +end:
>       mutex_unlock(&hook_mutex);
>  }
>  EXPORT_SYMBOL_GPL(battery_hook_register);
> @@ -732,7 +733,7 @@ EXPORT_SYMBOL_GPL(battery_hook_register);
>  */
>  static void battery_hook_add_battery(struct acpi_battery *battery)
>  {
> -     struct acpi_battery_hook *hook_node;
> +     struct acpi_battery_hook *hook_node, *tmp;
>  
>       mutex_lock(&hook_mutex);
>       INIT_LIST_HEAD(&battery->list);
> @@ -744,15 +745,15 @@ static void battery_hook_add_battery(struct 
> acpi_battery *battery)
>        * when a battery gets hotplugged or initialized
>        * during the battery module initialization.
>        */
> -     list_for_each_entry(hook_node, &battery_hook_list, list) {
> +     list_for_each_entry_safe(hook_node, tmp, &battery_hook_list, list) {
>               if (hook_node->add_battery(battery->bat)) {
>                       /*
>                        * The notification of the extensions has failed, to
>                        * prevent further errors we will unload the extension.
>                        */
> -                     __battery_hook_unregister(hook_node, 0);
>                       pr_err("error in extension, unloading: %s",
>                                       hook_node->name);
> +                     __battery_hook_unregister(hook_node, 0);
>               }
>       }
>       mutex_unlock(&hook_mutex);
> -- 
> 2.18.0
> 

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