As you know I have made the pre-timeout support patch, If people like
it, i am happy to go on upstream it separately.
If we want to use pre-timeout here, user only can use get_pretimeout
and disable panic by setting pretimeout to 0
but user can not really set pretimeout, because "pre-timeout ==
timeout / 2 (always)".
if user want to change pretimeout, he/she has to set_time instead.