linux-kernel - Re: [PATCH v3] usb: roles: add lockdep class key to struct usb_role

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Message-ID: <ZsiYRAJST/2hAju1@kuha.fi.intel.com>
Date: Fri, 23 Aug 2024 17:10:12 +0300
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Amit Sunil Dhamne <amitsd@...gle.com>
Cc: gregkh@...uxfoundation.org, badhri@...gle.com,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	kyletso@...gle.com, rdbabiera@...gle.com
Subject: Re: [PATCH v3] usb: roles: add lockdep class key to struct
 usb_role_switch

On Thu, Aug 22, 2024 at 03:37:15PM -0700, Amit Sunil Dhamne wrote:
> There can be multiple role switch devices running on a platform. Given
> that lockdep is not capable of differentiating between locks of
> different instances, false positive warnings for circular locking are
> reported. To prevent this, register unique lockdep key for each of the
> individual instances.
> 
> Signed-off-by: Amit Sunil Dhamne <amitsd@...gle.com>
> Reviewed-by: Badhri Jagan Sridharan <badhri@...gle.com>

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
> v1->v2
> - Avoid usage of ifdefs.
> v2->v3
> - Removed redundancies.
> - Completed peer review and added reviewer signature.
> ---
>  drivers/usb/roles/class.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
> index d7aa913ceb8a..7aca1ef7f44c 100644
> --- a/drivers/usb/roles/class.c
> +++ b/drivers/usb/roles/class.c
> @@ -11,6 +11,7 @@
>  #include <linux/usb/role.h>
>  #include <linux/property.h>
>  #include <linux/device.h>
> +#include <linux/lockdep.h>
>  #include <linux/module.h>
>  #include <linux/mutex.h>
>  #include <linux/slab.h>
> @@ -33,6 +34,8 @@ struct usb_role_switch {
>  	usb_role_switch_set_t set;
>  	usb_role_switch_get_t get;
>  	bool allow_userspace_control;
> +
> +	struct lock_class_key key;
>  };
>  
>  #define to_role_switch(d)	container_of(d, struct usb_role_switch, dev)
> @@ -396,6 +399,9 @@ usb_role_switch_register(struct device *parent,
>  
>  	sw->registered = true;
>  
> +	lockdep_register_key(&sw->key);
> +	lockdep_set_class(&sw->lock, &sw->key);
> +
>  	/* TODO: Symlinks for the host port and the device controller. */
>  
>  	return sw;
> @@ -412,6 +418,9 @@ void usb_role_switch_unregister(struct usb_role_switch *sw)
>  {
>  	if (IS_ERR_OR_NULL(sw))
>  		return;
> +
> +	lockdep_unregister_key(&sw->key);
> +
>  	sw->registered = false;
>  	if (dev_fwnode(&sw->dev))
>  		component_del(&sw->dev, &connector_ops);
> 
> base-commit: ca7df2c7bb5f83fe46aa9ce998b7352c6b28f3a1
> -- 
> 2.46.0.184.g6999bdac58-goog

-- 
heikki