Re: RFC: A revised timerfd API

Thomas Gleixner
2007-09-18T09:43:13Z

On Tue, 2007-09-18 at 11:30 +0200, Michael Kerrisk wrote:
> > This way we have it nicely integrated into the posix timer code and keep
> > the existing semantics of posix timers intact.
> >
> > We need to think about the open file descriptor in the timer_delete()
> > case as well, but this should be not too hard to sort out.
>
> This seems like a workable idea also. But note David Härdeman's
> critique of options c & d: the existence of a coupled timerfd
> and a timerid means that the application must maintain a mapping
> between the two, so that after an epoll call (for example) that
> says the timerfd is ready, the timer can be manipulated using
> the corresponding timerfd. This isn't IMO a fatal flaw, but
> it does make the API a little more clumsy.

Hmm, we might do something like:

timer_gettime(fd | POSIX_TIMER_FD, .....);

So the kernel looks up the fd in order to figure out the timer_id, which
needs to be referenced in filep->private_data anyway.

tglx