Re: Rationale for paccept() sigset argument?

["Michael Kerrisk" <mtk.manpages@googlemail.com>]

Ulrich -- ping!

---------- Forwarded message ----------
From: Michael Kerrisk <mtk.manpages@googlemail.com>
Date: Sep 2, 2008 9:58 AM
Subject: Re: Rationale for paccept() sigset argument?
To: Ulrich Drepper <drepper@gmail.com>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>, Ulrich Drepper
<drepper@redhat.com>, Davide Libenzi <davidel@xmailserver.org>, lkml
<linux-kernel@vger.kernel.org>, Andrew Morton
<akpm@linux-foundation.org>, Jakub Jelinek <jakub@redhat.com>, Linus
Torvalds <torvalds@linux-foundation.org>


Ulrich Drepper wrote:
> On Wed, Aug 20, 2008 at 9:50 AM, Michael Kerrisk
> <mtk.manpages@googlemail.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