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Date: Sat, 6 Apr 2024 20:57:00 +0200
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Subject: Re: [PATCH] platform/x86: quickstart: Fix race condition when
 reporting input event
From: Armin Wolf <W_Armin@gmx.de>
To: hdegoede@redhat.com, ilpo.jarvinen@linux.intel.com
Cc: rafael@kernel.org, linux-acpi@vger.kernel.org,
 platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org
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Am 27.03.24 um 22:45 schrieb Armin Wolf:

> Since commit e2ffcda16290 ("ACPI: OSL: Allow Notify () handlers to run
> on all CPUs"), the ACPI core allows multiple notify calls to be active
> at the same time. This means that two instances of quickstart_notify()
> running at the same time can mess which each others input sequences.
>
> Fix this by protecting the input sequence with a mutex.
>
> Compile-tested only.

Any thoughts on this?

Armin Wolf

> Fixes: afd66f2a739e ("platform/x86: Add ACPI quickstart button (PNP0C32) driver")
> Signed-off-by: Armin Wolf <W_Armin@gmx.de>
> ---
> This applies on the branch "review-hans". Maybe we could somehow
> document the concurrency rules for ACPI notify handlers?
> ---
>   drivers/platform/x86/quickstart.c | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
>
> diff --git a/drivers/platform/x86/quickstart.c b/drivers/platform/x86/quickstart.c
> index ba3a7a25dda7..e40f852d42c1 100644
> --- a/drivers/platform/x86/quickstart.c
> +++ b/drivers/platform/x86/quickstart.c
> @@ -18,6 +18,7 @@
>   #include <linux/input/sparse-keymap.h>
>   #include <linux/kernel.h>
>   #include <linux/module.h>
> +#include <linux/mutex.h>
>   #include <linux/platform_device.h>
>   #include <linux/sysfs.h>
>   #include <linux/types.h>
> @@ -35,6 +36,7 @@
>
>   struct quickstart_data {
>   	struct device *dev;
> +	struct mutex input_lock;	/* Protects input sequence during notify */
>   	struct input_dev *input_device;
>   	char input_name[32];
>   	char phys[32];
> @@ -73,7 +75,10 @@ static void quickstart_notify(acpi_handle handle, u32 event, void *context)
>
>   	switch (event) {
>   	case QUICKSTART_EVENT_RUNTIME:
> +		mutex_lock(&data->input_lock);
>   		sparse_keymap_report_event(data->input_device, 0x1, 1, true);
> +		mutex_unlock(&data->input_lock);
> +
>   		acpi_bus_generate_netlink_event(DRIVER_NAME, dev_name(data->dev), event, 0);
>   		break;
>   	default:
> @@ -147,6 +152,13 @@ static void quickstart_notify_remove(void *context)
>   	acpi_remove_notify_handler(handle, ACPI_DEVICE_NOTIFY, quickstart_notify);
>   }
>
> +static void quickstart_mutex_destroy(void *data)
> +{
> +	struct mutex *lock = data;
> +
> +	mutex_destroy(lock);
> +}
> +
>   static int quickstart_probe(struct platform_device *pdev)
>   {
>   	struct quickstart_data *data;
> @@ -165,6 +177,11 @@ static int quickstart_probe(struct platform_device *pdev)
>   	data->dev = &pdev->dev;
>   	dev_set_drvdata(&pdev->dev, data);
>
> +	mutex_init(&data->input_lock);
> +	ret = devm_add_action_or_reset(&pdev->dev, quickstart_mutex_destroy, &data->input_lock);
> +	if (ret < 0)
> +		return ret;
> +
>   	/* We have to initialize the device wakeup before evaluating GHID because
>   	 * doing so will notify the device if the button was used to wake the machine
>   	 * from S5.
> --
> 2.39.2
>
>