New "timeout" api, to replace callout

[Andre Oppermann]

Poul-Henning Kamp wrote:
> In message <477C2739.5000902 at freebsd.org>, Andre Oppermann writes:
>> Poul-Henning Kamp wrote:
>>> In message <477C1CF3.6070301 at freebsd.org>, Andre Oppermann writes:
>>>
>>>> I fear we have to go for the latter.  Getting a non-sleeping callout
>>>> drain seems to be non-trivial.
>>> There is a crucial difference between "non-sleeping" and "not sleeping
>>> on my lock" that you should be very careful about in this context.
>>>
>>> Which is your requirement ?
>> Calling timeout_drain() must not sleep and not drop the lock in this
>> context (while making any pending timeout go away forever).
> 
> Ok, so if the timeouts callback function is running you propose to
> do what ?  spin until it returns ?

As long as the spinning is bounded.  Or it may do some magic atomic
cmpset to tell the waiting timeout to give up.  Which then confirms
and timeout_drain then can return in peace.  Some (limited?) timeout
structure here may be outside of the tcpcb and get Gc'd by the timeout
system asynchronously after the drain.  I don't have a perfect solution
handy.  That's why I try to state the requirement and hope the timeout
gurus can work out how to do it.  ;-)

-- 
Andre