# Re: \[RFCv4\] timerfd: add TFD\_NOTIFY\_CLOCK\_SET to watch for clock changes

- From: Kay Sievers \<hidden\>
- Date: 2011-03-10 00:36:18 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2011/03/51532
- Thread: https://ratatoskr.run/linux-api/2011/03/51532/t.md

```text
On Thu, Mar 10, 2011 at 01:25, Andrew Morton [ref] wrote:
> On Wed,  9 Mar 2011 16:36:51 +0200
> Alexander Shishkin [ref] wrote:
>
>> Changes since v3:
>>  - changed timerfd_settime() semantics (see below)
>> Changes since v2:
>>  - replaced sysfs interface with a syscall
>>  - added sysctl/procfs handle to set a limit to the number of users
>>  - fixed issues pointed out by Greg.
>> Changes since v1:
>>  - updated against 2.6.36-rc1,
>>  - added notification/filtering options,
>>  - added Documentation/ABI/sysfs-kernel-time-notify interface description.

> It would be helpful to know if the identified users of this feature
> actually find it useful and adequate.  I guess the most common
> application is the 1,001 desktop clock widgets.  Do you have any
> feedback from any of the owners of those?

We want it for systemd, to provide cron-like functionality but without
the need to stupidly wake up every minute and check the system time
for possible jumps.

It also sounds useful for a generic resume (after system suspend)
notification for applications, which isn't really possible today.

Kay
```