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

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Date:   Mon, 5 Oct 2020 10:05:09 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     dmitry.torokhov@...il.com, "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Andrzej Pietrasiewicz <andrzej.p@...labora.com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI / button: fix handling lid state changes when input
 device closed

Hi,

On 10/5/20 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>

Patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@...hat.com>

Regards,

Hans


> ---
>   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);
>