Re: RFC: A revised timerfd API

[Thomas Gleixner <tglx@linutronix.de>]

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