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@vger.kernel.org
Signed-off-by: Elson Roy Serrao <quic_eserrao@quicinc.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Bug: 396434790
Link: https://lore.kernel.org/all/20250206193950.22421-1-quic_eserrao@quicinc.com/
Change-Id: I8d01033de48fc86ae935e609a172543066ea73d2
Signed-off-by: Elson Roy Serrao <quic_eserrao@quicinc.com>
Elson Roy Serrao
b0557422ff