linux-kernel - Re: [RESEND PATCH 5/6] input: usbtouchscreen: fix deadlock in autosuspend

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Date:   Sat, 17 Mar 2018 11:11:12 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Marcus Folkesson <marcus.folkesson@...il.com>
Cc:     Arvind Yadav <arvind.yadav.cs@...il.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH 5/6] input: usbtouchscreen: fix deadlock in
 autosuspend

On Wed, Feb 28, 2018 at 02:38:02PM +0100, Marcus Folkesson wrote:
> usb_autopm_get_interface() that is called in usbtouch_open() does an
> autoresume if the device is suspended.
> 
> input_dev->mutex used in usbtouch_resume() is in this case already
> taken by the input subsystem and will cause a deadlock.
> 
> Signed-off-by: Marcus Folkesson <marcus.folkesson@...il.com>

Applied, thank you.

> ---
>  drivers/input/touchscreen/usbtouchscreen.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
> index 2c41107240de..e964658203d8 100644
> --- a/drivers/input/touchscreen/usbtouchscreen.c
> +++ b/drivers/input/touchscreen/usbtouchscreen.c
> @@ -54,6 +54,7 @@
>  #include <linux/usb.h>
>  #include <linux/usb/input.h>
>  #include <linux/hid.h>
> +#include <linux/mutex.h>
>  
>  
>  #define DRIVER_VERSION		"v0.6"
> @@ -112,6 +113,7 @@ struct usbtouch_usb {
>  	struct usb_interface *interface;
>  	struct input_dev *input;
>  	struct usbtouch_device_info *type;
> +	struct mutex pm_mutex;  /* serialize access to open/suspend */
>  	char name[128];
>  	char phys[64];
>  	void *priv;
> @@ -1455,6 +1457,7 @@ static int usbtouch_open(struct input_dev *input)
>  	if (r < 0)
>  		goto out;
>  
> +	mutex_lock(&usbtouch->pm_mutex);
>  	if (!usbtouch->type->irq_always) {
>  		if (usb_submit_urb(usbtouch->irq, GFP_KERNEL)) {
>  			r = -EIO;
> @@ -1464,6 +1467,7 @@ static int usbtouch_open(struct input_dev *input)
>  
>  	usbtouch->interface->needs_remote_wakeup = 1;
>  out_put:
> +	mutex_unlock(&usbtouch->pm_mutex);
>  	usb_autopm_put_interface(usbtouch->interface);
>  out:
>  	return r;
> @@ -1474,8 +1478,11 @@ static void usbtouch_close(struct input_dev *input)
>  	struct usbtouch_usb *usbtouch = input_get_drvdata(input);
>  	int r;
>  
> +	mutex_lock(&usbtouch->pm_mutex);
>  	if (!usbtouch->type->irq_always)
>  		usb_kill_urb(usbtouch->irq);
> +	mutex_lock(&usbtouch->pm_mutex);
> +
>  	r = usb_autopm_get_interface(usbtouch->interface);
>  	usbtouch->interface->needs_remote_wakeup = 0;
>  	if (!r)
> @@ -1498,10 +1505,10 @@ static int usbtouch_resume(struct usb_interface *intf)
>  	struct input_dev *input = usbtouch->input;
>  	int result = 0;
>  
> -	mutex_lock(&input->mutex);
> +	mutex_lock(&usbtouch->pm_mutex);
>  	if (input->users || usbtouch->type->irq_always)
>  		result = usb_submit_urb(usbtouch->irq, GFP_NOIO);
> -	mutex_unlock(&input->mutex);
> +	mutex_unlock(&usbtouch->pm_mutex);
>  
>  	return result;
>  }
> @@ -1524,10 +1531,10 @@ static int usbtouch_reset_resume(struct usb_interface *intf)
>  	}
>  
>  	/* restart IO if needed */
> -	mutex_lock(&input->mutex);
> +	mutex_lock(&usbtouch->pm_mutex);
>  	if (input->users)
>  		err = usb_submit_urb(usbtouch->irq, GFP_NOIO);
> -	mutex_unlock(&input->mutex);
> +	mutex_unlock(&usbtouch->pm_mutex);
>  
>  	return err;
>  }
> -- 
> 2.16.2
> 

-- 
Dmitry