RFC: better timer interface

Arnd Bergmann arnd at arndb.de
Wed May 17 01:45:07 AEST 2017


On Tue, May 16, 2017 at 1:48 PM, Christoph Hellwig <hch at lst.de> wrote:
> Hi all,
>
> this series attempts to provide a "modern" timer interface where the
> callback gets the timer_list structure as an argument so that it
> can use container_of instead of having to cast to/from unsigned long
> all the time (or even worse use function pointer casts, we have quite
> a few of those as well).

This looks really nice, but what is the long-term plan for the interface?
Do you expect that we will eventually change all 700+ users of timer_list
to the new type, or do we keep both variants around indefinitely to avoid
having to do mass-conversions?

If we are going to touch them all in the end, we might want to think
about other changes that could be useful here. The main one I have
in mind would be moving away from 'jiffies + timeout' as the interface,
and instead passing a relative number of milliseconds (or seconds)
into a mod_timer() variant. This is what most drivers want anyway,
and if we have both changes (callback argument and expiration
time) in place, we modernize the API one driver at a time with both
changes at once.

      Arnd


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