Re: [PATCHv6 1/7] notify userspace about time changes

[Arnd Bergmann <arnd@arndb.de>]

On Thursday 11 November 2010 20:29:56 Alexander Shishkin wrote:
> Certain userspace applications (like "clock" desktop applets or cron) 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;
>  - changing system timekeeping policy for system-wide time management
>    programs;
>  - keeping guest applications/operating systems running in emulators
>    up to date.
> 
> This patch implements a notification interface via eventfd mechanism. Proccess
> wishing to be notified about time changes should create an eventfd and pass it
> to time_change_notify() syscall. After that, any calls to settimeofday()/
> stime()/adjtimex() made by other processes will be signalled to this eventfd.
> Credits for suggesting the eventfd mechanism for this purpose go to Kirill
> Shutemov.
> 
> This patch adds the syscall to asm-generic/unistd.h and a simple usage
> example.

Looks reasonable to me.

It would be good to have the man page for this, too. I guess it could
be added to the existing clock_{get,set}time man page, so you can
add a patch for that.

	Arnd