linux-kernel - Re: Rationale for paccept() sigset argument?

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Message-ID: <cfd18e0f0809102248l4f13e43h6c17d0a8915dc9c8@mail.gmail.com>
Date:	Thu, 11 Sep 2008 07:48:56 +0200
From:	"Michael Kerrisk" <mtk.manpages@...glemail.com>
To:	"Ulrich Drepper" <drepper@...il.com>
Cc:	"Roland McGrath" <roland@...hat.com>,
	"Michael Kerrisk" <mtk.manpages@...glemail.com>,
	"Davide Libenzi" <davidel@...ilserver.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Jakub Jelinek" <jakub@...hat.com>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>
Subject: Re: Rationale for paccept() sigset argument?

[CC+=Roland]

On 9/2/08, Michael Kerrisk <mtk.manpages@...glemail.com> wrote:
> Ulrich Drepper wrote:
> > On Wed, Aug 20, 2008 at 9:50 AM, Michael Kerrisk
> > <mtk.manpages@...glemail.com> wrote:
> >
> > > What is the rationale for the sigset argument of paccept()?
> > >
> >
> > accept, like select/poll, is used often as a function to dealy
> > operation.  Unlike read, recv, etc, which are handled using O_NONBLOCK
> > and select/poll.  pselect/ppoll do not really have a sigset parameter
> > to handle signals in general.  You use it to enable special handling
> > in case of blocking.  Example: if you want to implement userlevel
> > context switching, you dedicate a signal to wake up any blocked
> > thread.  Since accept falls more into the same category than poll,
> > this means the sigset parameter is justified.  In theory we could add
> > it to all functions but there is no reason to do this without any
> > other reason to change the interface.
> >
>
>
> Ulrich, you snipped a relevant piece of my earlier message:
>
> [[
> > * It seems to me that any case where we might want to use paccept() could
> be
> > equivalently dealt with using the existing
> pselect()/ppoll()/epoll_pwait()
> > followed by a conventional accept() if the listening file descriptor
> > indicates as ready.
> ]]
>
> So I'll rephrase: what use case does the sigset argument of paccept()
> allow us to handle that couldn't equally have been handled by
> pselect()/ppoll()/epoll_pwait() + traditional accept()?
>
>
> Cheers,
>
> Michael
>
> --
> Michael Kerrisk
> Linux man-pages maintainer;
> http://www.kernel.org/doc/man-pages/
> man-pages online:
> http://www.kernel.org/doc/man-pages/online_pages.html
> Found a bug?
> http://www.kernel.org/doc/man-pages/reporting_bugs.html
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