Messages in this thread | | | Date | Tue, 2 Apr 2024 16:13:30 +0200 | Subject | Re: [PATCH 2/4] platform/x86: xiaomi-wmi: Fix race condition when reporting key events | From | Armin Wolf <> |
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Am 29.03.24 um 02:37 schrieb Kuppuswamy Sathyanarayanan:
> On 3/28/24 5:26 PM, Armin Wolf wrote: >> Am 28.03.24 um 03:58 schrieb Kuppuswamy Sathyanarayanan: >> >>> On 3/27/24 6:23 PM, Armin Wolf wrote: >>>> Multiple WMI events can be received concurrently, so multiple instances >>>> of xiaomi_wmi_notify() can be active at the same time. Since the input >>>> device is shared between those handlers, the key input sequence can be >>>> disturbed. >>> Since locking is needed for all notify related calls in all WMI drivers, >>> is there a generic way to add this support in WMI core driver? Like >>> defining some common function which will hold the lock and call >>> driver specific notify handler? I am just thinking aloud.. If it is not >>> feasible, then it is fine. >> Hi, >> >> actually, not all notify-related calls need locking. It just so happens that >> input drivers must protect their key sequence, other WMI drivers might not need >> to use any locking at all. > Got it. > >> I would prefer if the WMI driver does the locking, so it can be optimized for >> each WMI driver. > Why not implement this support?
Because different WMI drivers will most certainly have different need when it comes to locking. Some might want to use a simple mutex, some might want to use a RW-lock, and others might need something totally different.
Implementing all of this inside the WMI driver core will be difficult.
Thanks, Armin Wolf
>> Thanks, >> Armin Wolf >> >>>> Fix this by protecting the key input sequence with a mutex. >>>> >>>> Compile-tested only. >>>> >>>> Fixes: edb73f4f0247 ("platform/x86: wmi: add Xiaomi WMI key driver") >>>> Signed-off-by: Armin Wolf <W_Armin@gmx.de> >>>> --- >>>> drivers/platform/x86/xiaomi-wmi.c | 18 ++++++++++++++++++ >>>> 1 file changed, 18 insertions(+) >>>> >>>> diff --git a/drivers/platform/x86/xiaomi-wmi.c b/drivers/platform/x86/xiaomi-wmi.c >>>> index 1f5f108d87c0..7efbdc111803 100644 >>>> --- a/drivers/platform/x86/xiaomi-wmi.c >>>> +++ b/drivers/platform/x86/xiaomi-wmi.c >>>> @@ -2,8 +2,10 @@ >>>> /* WMI driver for Xiaomi Laptops */ >>>> >>>> #include <linux/acpi.h> >>>> +#include <linux/device.h> >>>> #include <linux/input.h> >>>> #include <linux/module.h> >>>> +#include <linux/mutex.h> >>>> #include <linux/wmi.h> >>>> >>>> #include <uapi/linux/input-event-codes.h> >>>> @@ -20,12 +22,21 @@ >>>> >>>> struct xiaomi_wmi { >>>> struct input_dev *input_dev; >>>> + struct mutex key_lock; /* Protects the key event sequence */ >>>> unsigned int key_code; >>>> }; >>>> >>>> +static void xiaomi_mutex_destroy(void *data) >>>> +{ >>>> + struct mutex *lock = data; >>>> + >>>> + mutex_destroy(lock); >>>> +} >>>> + >>>> static int xiaomi_wmi_probe(struct wmi_device *wdev, const void *context) >>>> { >>>> struct xiaomi_wmi *data; >>>> + int ret; >>>> >>>> if (wdev == NULL || context == NULL) >>>> return -EINVAL; >>>> @@ -35,6 +46,11 @@ static int xiaomi_wmi_probe(struct wmi_device *wdev, const void *context) >>>> return -ENOMEM; >>>> dev_set_drvdata(&wdev->dev, data); >>>> >>>> + mutex_init(&data->key_lock); >>>> + ret = devm_add_action_or_reset(&wdev->dev, xiaomi_mutex_destroy, &data->key_lock); >>>> + if (ret < 0) >>>> + return ret; >>>> + >>>> data->input_dev = devm_input_allocate_device(&wdev->dev); >>>> if (data->input_dev == NULL) >>>> return -ENOMEM; >>>> @@ -59,10 +75,12 @@ static void xiaomi_wmi_notify(struct wmi_device *wdev, union acpi_object *dummy) >>>> if (data == NULL) >>>> return; >>>> >>>> + mutex_lock(&data->key_lock); >>>> input_report_key(data->input_dev, data->key_code, 1); >>>> input_sync(data->input_dev); >>>> input_report_key(data->input_dev, data->key_code, 0); >>>> input_sync(data->input_dev); >>>> + mutex_unlock(&data->key_lock); >>>> } >>>> >>>> static const struct wmi_device_id xiaomi_wmi_id_table[] = { >>>> -- >>>> 2.39.2 >>>> >>>>
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