linux-kernel - Re: [PATCH] ACPI / button: fix handling lid state changes when input device closed

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Date:   Mon, 5 Oct 2020 13:29:05 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Hans de Goede <hdegoede@...hat.com>,
        Andrzej Pietrasiewicz <andrzej.p@...labora.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI / button: fix handling lid state changes when input
 device closed

On Mon, Oct 5, 2020 at 7:11 AM <dmitry.torokhov@...il.com> wrote:
>
> The original intent of 84d3f6b76447 was to delay evaluating lid state until
> all drivers have been loaded, with input device being opened from userspace
> serving as a signal for this condition. Let's ensure that state updates
> happen even if userspace closed (or in the future inhibited) input device.
>
> Note that if we go through suspend/resume cycle we assume the system has
> been fully initialized even if LID input device has not been opened yet.
>
> This has a side-effect of fixing access to input->users outside of
> input->mutex protections by the way of eliminating said accesses and using
> driver private flag.
>
> Fixes: 84d3f6b76447 ("ACPI / button: Delay acpi_lid_initialize_state() until first user space open")
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> ---
>  drivers/acpi/button.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
> index 78cfc70cb320..b8dd51d8f96d 100644
> --- a/drivers/acpi/button.c
> +++ b/drivers/acpi/button.c
> @@ -154,6 +154,7 @@ struct acpi_button {
>         int last_state;
>         ktime_t last_time;
>         bool suspended;
> +       bool lid_state_initialized;
>  };
>
>  static struct acpi_device *lid_device;
> @@ -384,6 +385,8 @@ static int acpi_lid_update_state(struct acpi_device *device,
>
>  static void acpi_lid_initialize_state(struct acpi_device *device)
>  {
> +       struct acpi_button *button = acpi_driver_data(device);
> +
>         switch (lid_init_state) {
>         case ACPI_BUTTON_LID_INIT_OPEN:
>                 (void)acpi_lid_notify_state(device, 1);
> @@ -395,13 +398,14 @@ static void acpi_lid_initialize_state(struct acpi_device *device)
>         default:
>                 break;
>         }
> +
> +       button->lid_state_initialized = true;
>  }
>
>  static void acpi_button_notify(struct acpi_device *device, u32 event)
>  {
>         struct acpi_button *button = acpi_driver_data(device);
>         struct input_dev *input;
> -       int users;
>
>         switch (event) {
>         case ACPI_FIXED_HARDWARE_EVENT:
> @@ -410,10 +414,7 @@ static void acpi_button_notify(struct acpi_device *device, u32 event)
>         case ACPI_BUTTON_NOTIFY_STATUS:
>                 input = button->input;
>                 if (button->type == ACPI_BUTTON_TYPE_LID) {
> -                       mutex_lock(&button->input->mutex);
> -                       users = button->input->users;
> -                       mutex_unlock(&button->input->mutex);
> -                       if (users)
> +                       if (button->lid_state_initialized)
>                                 acpi_lid_update_state(device, true);
>                 } else {
>                         int keycode;
> @@ -458,7 +459,7 @@ static int acpi_button_resume(struct device *dev)
>         struct acpi_button *button = acpi_driver_data(device);
>
>         button->suspended = false;
> -       if (button->type == ACPI_BUTTON_TYPE_LID && button->input->users) {
> +       if (button->type == ACPI_BUTTON_TYPE_LID) {
>                 button->last_state = !!acpi_lid_evaluate_state(device);
>                 button->last_time = ktime_get();
>                 acpi_lid_initialize_state(device);
> --

Applied as 5.10 material with the R-by from Hans, thanks!