[PATCH v3] usb: roles: add lockdep class key to struct usb_role_switch

[PATCH v3] usb: roles: add lockdep class key to struct usb_role_switch

[Amit Sunil Dhamne]

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@google.com>
Reviewed-by: Badhri Jagan Sridharan <badhri@google.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

Re: [PATCH v3] usb: roles: add lockdep class key to struct usb_role_switch

[Heikki Krogerus]

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@google.com>
> Reviewed-by: Badhri Jagan Sridharan <badhri@google.com>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.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