Messages in this thread | | | From | Kay Sievers <> | Date | Fri, 6 Aug 2010 00:22:27 +0200 | Subject | Re: [PATCH] [RFC] notify userspace about time changes |
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On Thu, Aug 5, 2010 at 23:38, Greg KH <gregkh@suse.de> wrote: > On Thu, Aug 05, 2010 at 02:11:05PM -0700, john stultz wrote: >> On Thu, 2010-08-05 at 15:33 +0300, Alexander Shishkin wrote: >> > On 4 August 2010 18:58, john stultz <johnstul@us.ibm.com> wrote: >> > > Is there a actual use case that you need this for? I don't really have >> > > an issue with the code I just really want to make sure the feature would >> > > be useful enough to justify the API and code maintenance going forward. >> > >> > Yes. What we have here is an application which takes care of different means >> > of time synchronization (trusted time servers, different GSM operators, etc) >> > and also different kinds of time-based events/notifications (like "dentist >> > appointment next thursday"). When it encounters a time change that is >> > made by some other application, it basically wants to disable automatic >> > time adjustment and trigger the events/notifications which are due at this >> > (new) time. >> >> Ok. Something specific is always more helpful then theoretical uses. >> >> I think the filtering is still a bit controversial, so you might want to >> respin it without that. But otherwise I'm ok with it as long as no one >> else objects to any of the minor details of the interface >> >> GregKH: Does /sys/kernel/time_notify seem ok by you? > > Um, it depends, what is that file going to do? I don't see a > Documentation/ABI/ entry here that describes it fully :)
I think that's really awkward interface, to pass file descriptor numbers around and write them to magic sysfs files.
I would very much prefer a file that contains the current time, and wakes up possible users with a POLL_ERR on changes caused by some other process. That works very well for things like /proc/mounts, is easy to get, and does not need a full page of weird instructions to get stuff done. :)
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