Messages in this thread | | | Subject | Re: [PATCH] [RFC] timerfd: add TFD_NOTIFY_CLOCK_SET to watch for clock changes | From | Artem Bityutskiy <> | Date | Wed, 24 Nov 2010 10:05:35 +0200 |
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On Tue, 2010-11-23 at 23:43 +0100, Lennart Poettering wrote: > On Tue, 23.11.10 19:22, Alexander Shishkin (virtuoso@slind.org) wrote: > > > Certain userspace applications (like "clock" desktop applets or cron or > > systemd) might want to be notified when some other application changes > > the system time. There are several known to me reasons for this: > > - avoiding periodic wakeups to poll time changes; > > - rearming CLOCK_REALTIME timers when said changes happen; > > - changing system timekeeping policy for system-wide time management > > programs; > > - keeping guest applications/operating systems running in emulators > > up to date. > > > > This is another attempt to approach notifying userspace about system > > clock changes. The other one is using an eventfd and a syscall [1]. In > > the course of discussing the necessity of a syscall for this kind of > > notifications, it was suggested that this functionality can be achieved > > via timers [2] (and timerfd in particular [3]). This idea got quite > > some support [4], [5], [6] and some vague criticism [7], so I decided > > to try and go a bit further with it. > > I agree with Kay, this is pretty much exactly what we want for > systemd. (Assuming that the time jump due to system suspend is > propagated to userspace like any other time jump with this path).
A "Tested-by: Lennart Poettering <mzxreary@0pointer.de>" would be helpful, I think.
> So yeah, I'd be very happy if this could be merged.
Hmm, and question about why exactly the timerfd interface is a bad way to go was ignored.
-- Best Regards, Artem Bityutskiy (Артём Битюцкий)
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