Commit 634775a7 authored by Elson Roy Serrao's avatar Elson Roy Serrao Committed by Greg Kroah-Hartman
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usb: roles: set switch registered flag early on 



The role switch registration and set_role() can happen in parallel as they
are invoked independent of each other. There is a possibility that a driver
might spend significant amount of time in usb_role_switch_register() API
due to the presence of time intensive operations like component_add()
which operate under common mutex. This leads to a time window after
allocating the switch and before setting the registered flag where the set
role notifications are dropped. Below timeline summarizes this behavior

Thread1				|	Thread2
usb_role_switch_register()	|
	|			|
	---> allocate switch	|
	|			|
	---> component_add()	|	usb_role_switch_set_role()
	|			|	|
	|			|	--> Drop role notifications
	|			|	    since sw->registered
	|			|	    flag is not set.
	|			|
	--->Set registered flag.|

To avoid this, set the registered flag early on in the switch register
API.

Fixes: b787a3e7 ("usb: roles: don't get/set_role() when usb_role_switch is unregistered")
Cc: stable <stable@kernel.org>
Signed-off-by: default avatarElson Roy Serrao <quic_eserrao@quicinc.com>
Reviewed-by: default avatarHeikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20250206193950.22421-1-quic_eserrao@quicinc.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e5644be4

drivers/usb/roles/class.c

+3 −2
Original line number Diff line number Diff line
@@ -387,8 +387,11 @@ usb_role_switch_register(struct device *parent, 
	dev_set_name(&sw->dev, "%s-role-switch",

		     desc->name ? desc->name : dev_name(parent));



	sw->registered = true;



	ret = device_register(&sw->dev);

	if (ret) {

		sw->registered = false;

		put_device(&sw->dev);

		return ERR_PTR(ret);

	}
@@ -399,8 +402,6 @@ usb_role_switch_register(struct device *parent, 
			dev_warn(&sw->dev, "failed to add component\n");

	}



	sw->registered = true;



	/* TODO: Symlinks for the host port and the device controller. */



	return sw;