RFC: better timer interface

[David Laight]

From: Thomas Gleixner
> Sent: 21 May 2017 19:15
...
> > timer_start(timer, ms, abs)
> 
> I'm not even sure, whether we need absolute timer wheel timers at
> all, because most use cases are relative to now.

Posix requires absolute timers for some userspace calls
(annoying because the code often wants relative).

OTOH how much conditional code is there for the 'abs' argument.
And is there any code that doesn't pass a constant?

Certainly worth a separate timer_start_abs(timer, wall_time)
function since you can't correctly map a wall_time timer
to a jiffies one.

	David