linux-kernel - Re: [RESEND][RFC PATCH v2] waitfd

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Message-ID: <alpine.DEB.1.10.0901071259210.17115@alien.or.mcafeemobile.com>
Date:	Wed, 7 Jan 2009 13:05:45 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Roland McGrath <roland@...hat.com>,
	Casey Dahlin <cdahlin@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RESEND][RFC PATCH v2] waitfd

On Wed, 7 Jan 2009, Ingo Molnar wrote:

> 
> * Roland McGrath <roland@...hat.com> wrote:
> 
> > New syscall should have gone to linux-api, I think.
> > 
> > Do we really need another one for this?  How about using signalfd plus 
> > setting the child's exit_signal to a queuing (SIGRTMIN+n) signal instead 
> > of SIGCHLD?  It's slightly more magical for the userland process to know 
> > to do that (fork -> clone SIGRTMIN).  But compared to adding a syscall 
> > we don't really have to add, maybe better.
> 
> hm, i think it's cleaner conceptually than trying to wrap this into 
> signalfd. Since we already have:
> 
>   #define __NR_signalfd           321
>   #define __NR_timerfd_create     322
>   #define __NR_timerfd_settime    325
>   #define __NR_timerfd_gettime    326
>   #define __NR_signalfd4          327
> 
> is one more really such an issue?

And what did eventfd do to you? :)
I partially agree with Roland (and I stated this during Casey's first 
post), this can be achieved in a not too troublesome way already.
A new dedicated interface is easier for the challenged userspace coder, 
but I dunno if it's worth the new code (although it does have little 
footprint). Both ways are fine from my POV.



- Davide


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