USB: make single lock for all usb dynamic id lists

There are a number of places where we accidentally pass in a constant
structure to later cast it off to a dynamic one, and then attempt to
grab a lock on it, which is not a good idea.  To help resolve this, move
the dynamic id lock out of the dynamic id structure for the driver and
into one single lock for all USB dynamic ids.  As this lock should never
have any real contention (it's only every accessed when a device is
added or removed, which is always serialized) there should not be any
difference except for some memory savings.

Note, this just converts the existing use of the dynamic id lock to the
new static lock, there is one place that is accessing the dynamic id
list without grabbing the lock, that will be fixed up in a follow-on
change.

Cc: Johan Hovold <johan@kernel.org>
Cc: Herve Codina <herve.codina@bootlin.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Grant Grundler <grundler@chromium.org>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: Yajun Deng <yajun.deng@linux.dev>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: linux-usb@vger.kernel.org
Link: https://lore.kernel.org/r/2024111322-kindly-finalist-d247@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 2 insertions, 6 deletions

diff --git a/drivers/usb/serial/bus.c b/drivers/usb/serial/bus.c
index d200e2c29a8f..2fea1b1db4a2 100644
--- a/drivers/usb/serial/bus.c
+++ b/drivers/usb/serial/bus.c
@@ -136,12 +136,11 @@ static void free_dynids(struct usb_serial_driver *drv)
 {
 	struct usb_dynid *dynid, *n;
 
-	spin_lock(&drv->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry_safe(dynid, n, &drv->dynids.list, node) {
 		list_del(&dynid->node);
 		kfree(dynid);
 	}
-	spin_unlock(&drv->dynids.lock);
 }
 
 const struct bus_type usb_serial_bus_type = {
@@ -157,7 +156,6 @@ int usb_serial_bus_register(struct usb_serial_driver *driver)
 	int retval;
 
 	driver->driver.bus = &usb_serial_bus_type;
-	spin_lock_init(&driver->dynids.lock);
 	INIT_LIST_HEAD(&driver->dynids.list);
 
 	retval = driver_register(&driver->driver);
diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index df6a2ae0bf42..7266558d823a 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -706,14 +706,12 @@ static const struct usb_device_id *match_dynamic_id(struct usb_interface *intf,
 {
 	struct usb_dynid *dynid;
 
-	spin_lock(&drv->dynids.lock);
+	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry(dynid, &drv->dynids.list, node) {
 		if (usb_match_one_id(intf, &dynid->id)) {
-			spin_unlock(&drv->dynids.lock);
 			return &dynid->id;
 		}
 	}
-	spin_unlock(&drv->dynids.lock);
 	return NULL;
 }