linux-kernel - Re: [PATCH] Revised timerfd() interface

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Date:	Wed, 5 Sep 2007 09:14:12 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Michael Kerrisk <mtk-manpages@....net>
cc:	rdunlap@...otime.net, tglx@...utronix.de,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ulrich Drepper <drepper@...hat.com>, stable@...nel.org,
	hch@....de, jengelh@...putergmbh.de, corbet@....net,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] Revised timerfd() interface

On Wed, 5 Sep 2007, Michael Kerrisk wrote:

> Davide,

A Michael!


> > > As I think about this more, I see more problems with
> > > your argument.  timerfd needs the ability to get and 
> > > get-while-setting just as much as the earlier APIs.
> > > Consider a library that creates a timerfd file descriptor that
> > > is handed off to an application: that library may want
> > > to modify the timer settings without having to create a
> > > new file descriptor (the app mey not be able to be told about
> > > the new fd).  Your argument just doesn't hold, AFAICS.
> > 
> > Such hypotethical library, in case it really wanted to offer such 
> > functionality, could simply return an handle instead of the raw fd, and 
> > take care of all that stuff in userspace.
> 
> Did I miss something?  Is it not the case that as soon as the
> library returns a handle, rather than an fd, then the whole
> advantage of timerfd() (being able to select/poll/epoll on 
> the timer as well as other fds) is lost?  

Why? The handle would simply be a little struct where the timerfd fd is 
stored, and a XXX_getfd() would return it.
So my point is, I doubt such functionalities are really needed, and I also 
argue that the kernel is the best place for such wrapper code to go.



- Davide


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