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

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Date:	Tue, 02 Sep 2008 09:58:09 +0200
From:	Michael Kerrisk <mtk.manpages@...glemail.com>
To:	Ulrich Drepper <drepper@...il.com>
CC:	Michael Kerrisk <mtk.manpages@...glemail.com>,
	Ulrich Drepper <drepper@...hat.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?

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/
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