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usb: roles: set switch registered flag early on

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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: b787a3e781 ("usb: roles: don't get/set_role() when usb_role_switch is unregistered")
Cc: stable <stable@kernel.org>
Signed-off-by: Elson Roy Serrao <quic_eserrao@quicinc.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20250206193950.22421-1-quic_eserrao@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Elson Roy Serrao 2025-02-06 11:39:50 -08:00 • committed by Greg Kroah-Hartman
parent e5644be407
commit 634775a752
1 changed files with 3 additions and 2 deletions
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5
drivers/usb/roles/class.c
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@ -387,8 +387,11 @@ usb_role_switch_register(struct device *parent,
dev_set_name(&sw->dev, "%s-role-switch", dev_set_name(&sw->dev, "%s-role-switch",
desc->name ? desc->name : dev_name(parent)); desc->name ? desc->name : dev_name(parent));
sw->registered = true;
ret = device_register(&sw->dev); ret = device_register(&sw->dev);
if (ret) { if (ret) {
sw->registered = false;
put_device(&sw->dev); put_device(&sw->dev);
return ERR_PTR(ret); return ERR_PTR(ret);
} }
@ -399,8 +402,6 @@ usb_role_switch_register(struct device *parent,
dev_warn(&sw->dev, "failed to add component\n"); dev_warn(&sw->dev, "failed to add component\n");
} }
sw->registered = true;
/* TODO: Symlinks for the host port and the device controller. */ /* TODO: Symlinks for the host port and the device controller. */
return sw; return sw;