Messages in this thread | | | Date | Fri, 6 Aug 2010 09:43:44 +0200 | Subject | Re: [PATCH] [RFC] notify userspace about time changes | From | Bastien ROUCARIES <> |
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On Fri, Aug 6, 2010 at 12:22 AM, Kay Sievers <kay.sievers@vrfy.org> wrote: > 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. :) > See http://lwn.net/Articles/323658/ and it is plan9 compatible
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