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

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Date:	Tue, 04 Sep 2007 17:39:40 +0200
From:	"Michael Kerrisk" <mtk-manpages@....net>
To:	Davide Libenzi <davidel@...ilserver.org>, akpm@...ux-foundation.org
Cc:	corbet@....net, jengelh@...putergmbh.de, hch@....de,
	stable@...nel.org, drepper@...hat.com,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, rdunlap@...otime.net
Subject: Re: [PATCH] Revised timerfd() interface

Hi Davide,

> > <wakes up>
> > 
> > I'd have thought that the existing stuff would be near-useless without
> > the capabilities which you describe?
> 
> Useless like it'd be a motorcycle w/out a cup-holder :)
> Seriously, the ability to get the previous values from "something" could 
> have a meaning if this something is a shared global resource (like 
> signals
> for example). In the timerfd case this makes little sense, since you can 
> create as many timerfd as you like and you do not need to share a single 
> one by changing/restoring the original context.

However, one can have multipe POSIX timers, just as you can 
have multiple timerfd timers; nevertheless POSIX timers provide
the get and get-while-setting functionality.

> On top of that, the cup-holder addition would cost in terms of API 
> clarity

I agree my proposed API is not as clean as it could be, that's why
I would favour:

> (or in terms of two additional system calls in the other case),

Or better still, have timerfd() integrated with POSIX tiemrs (if
this is feasible).  This givesus a simple API, exactly one new
syscall, and all of the functionality of the existing POSIX
timers API.

> and in terms of kernel code footprint.

Not sure what your concern is here.  The total amount of 
new code for all of these options is pretty small.

Cheers,

Michael
-- 
Michael Kerrisk
maintainer of Linux man pages Sections 2, 3, 4, 5, and 7 

Want to help with man page maintenance?  
Grab the latest tarball at
http://www.kernel.org/pub/linux/docs/manpages , 
read the HOWTOHELP file and grep the source 
files for 'FIXME'.

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