rxrpc_try_get_call
struct rxrpc_call *rxrpc_try_get_call(struct rxrpc_call *, enum rxrpc_call_trace);
if (!busy && !rxrpc_try_get_call(call, rxrpc_call_get_poke))
call = rxrpc_try_get_call(chan->call, rxrpc_call_get_input);