Bluetooth: iso: Fix recursive locking warning

This updates iso_sock_accept to use nested locking for the parent
socket, to avoid lockdep warnings caused because the parent and
child sockets are locked by the same thread:

[   41.585683] ============================================
[   41.585688] WARNING: possible recursive locking detected
[   41.585694] 6.12.0-rc6+ torvalds#22 Not tainted
[   41.585701] --------------------------------------------
[   41.585705] iso-tester/3139 is trying to acquire lock:
[   41.585711] ffff988b29530a58 (sk_lock-AF_BLUETOOTH)
               at: bt_accept_dequeue+0xe3/0x280 [bluetooth]
[   41.585905]
               but task is already holding lock:
[   41.585909] ffff988b29533a58 (sk_lock-AF_BLUETOOTH)
               at: iso_sock_accept+0x61/0x2d0 [bluetooth]
[   41.586064]
               other info that might help us debug this:
[   41.586069]  Possible unsafe locking scenario:

[   41.586072]        CPU0
[   41.586076]        ----
[   41.586079]   lock(sk_lock-AF_BLUETOOTH);
[   41.586086]   lock(sk_lock-AF_BLUETOOTH);
[   41.586093]
                *** DEADLOCK ***

[   41.586097]  May be due to missing lock nesting notation

[   41.586101] 1 lock held by iso-tester/3139:
[   41.586107]  #0: ffff988b29533a58 (sk_lock-AF_BLUETOOTH)
                at: iso_sock_accept+0x61/0x2d0 [bluetooth]

Signed-off-by: Iulia Tanasescu <iulia.tanasescu@nxp.com>

net/bluetooth/iso.c

@@ -1241,7 +1241,11 @@ static int iso_sock_accept(struct socket *sock, struct socket *newsock,
 	long timeo;
 	int err = 0;
 
-	lock_sock(sk);
+	/* Use explicit nested locking to avoid lockdep warnings generated
+	 * because the parent socket and the child socket are locked on the
+	 * same thread.
+	 */
+	lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
 
 	timeo = sock_rcvtimeo(sk, arg->flags & O_NONBLOCK);
 
@@ -1272,7 +1276,7 @@ static int iso_sock_accept(struct socket *sock, struct socket *newsock,
 		release_sock(sk);
 
 		timeo = wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
-		lock_sock(sk);
+		lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
 	}
 	remove_wait_queue(sk_sleep(sk), &wait);