[lkml]   [2017]   [May]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: RFC: better timer interface
On Tue, May 16, 2017 at 5:51 PM, Christoph Hellwig <> wrote:
> On Tue, May 16, 2017 at 05:45:07PM +0200, Arnd Bergmann wrote:
>> 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?
> I think we should eventually move everyone over, but it might take
> some time.


>> 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.
> Yes, that sounds useful to me as well. As you said it's an independent
> but somewhat related change. I can add it to my series, but I'll
> need a suggestions for a good and short name. That already was the
> hardest part for the setup side :)

If we keep the unusual *_timer() naming (rather than timer_*() as hrtimer
has), we could use one of

a) start_timer(struct timer_list *timer, unsigned long ms);
b) restart_timer(struct timer_list *timer, unsigned long ms);
c) mod_timer_ms(struct timer_list *timer, unsigned long ms);
mod_timer_sec(struct timer_list *timer, unsigned long sec);

The first is slightly shorter but conflicts with three files that use
the same name for a local function name. The third one fits
well with the existing interfaces and provides both millisecond
and second versions, I'd probably go with that.

We could consider even passing a default interval as another
argument to prepare_timer(), and using that in add_timer(),
but that would in those cases that have a constant interval
(maybe about half of the users from) and would be a bit surprising
to readers that are only familiar with the existing interfaces.

One final option would be a larger-scale replacement of
the API by mirroring the hrtimer style where possible while
staying compatible with the existing calls, e.g. timer_prepare(),
timer_add_expires(), timer_start(), ...


 \ /
  Last update: 2017-05-16 22:27    [W:0.102 / U:8.672 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site