Re: Why does timerfd() only support CLOCK_REALTIME and CLOCK_MONOTONIC?

Davide Libenzi
2009-02-08T19:29:45Z

On Mon, 9 Feb 2009, Michael Kerrisk wrote:

> Hi Davide,
>
> At the moment I'm looking into writing man pages for timer_create(2)
> and friends. (Somewhat bizarrely, these pages do not yet exist.) As
> I looked into the source code of timer_create(), etc., and did some
> tests, I saw that timer_create() supports the following clocks:
>
> TIMER_REALTIME
> TIMER_MONOTONIC
> TIMER_PROCESS_CPUTIME_ID
> TIMER_THREAD_CPUTIME_ID
> clockid obtained from clock_getcpuclockid(3)
> clockid obtained from pthread_getcpuclockid(3)
>
> On the other hand, timerfd() only permits the first two of these.
> What's the reason for that limitation of timerfd()? (It may be worth
> adding something to the man page on this point.)

No particular reason I can think of. If Thomas makes invalid_clockid()
available, we could allow timerfd() to support all time timers
timer_create() supports.
Do you see any reason why this won't work Thomas?

- Davide