From: Michael Kerrisk <mtk.manpages@googlemail.com>
To: Ulrich Drepper <drepper@redhat.com>
Cc: 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>
Subject: Rationale for paccept() sigset argument?
Date: Wed, 20 Aug 2008 18:50:12 +0200 [thread overview]
Message-ID: <48AC4B44.2010606@gmail.com> (raw)
Ulrich,
I'll need to cover this point in the man pages, and the rationale still isn't
clear to me, so I'll check it with you...
2.6.27-rc has paccept():
int paccept(int fd, struct sockaddr *sockaddr, socklen_t *addrlen,
const sigset_t *sigmask, int setsize, int flags)
paccept() blocks until either a connection is received on fd, or a signal is
sigmask() is caught.
What is the rationale for the sigset argument of paccept()?
For pselect()/ppoll()/epoll_pwait(), the sigset argument allows us to deal
with a not uncommon situation: waiting for both signals and (multiple) file
descriptors. (The alternative is the self-pipe trick, which requires more
programming effort.)
However, do we really need this argument for paccept()? I ask this for the
following reasons:
* This seems to be special casing for accept(). But there are other system
calls (e.g., open(), connect(), recvfrom()) that are similar, in the sense
that they may wait on a file descriptor, for which there is no [perceived
need for a] sigset argument.
* 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. (But perhaps I missed something?)
Can you please explain why we need this special case for [p]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
next reply other threads:[~2008-08-20 16:54 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-20 16:50 Michael Kerrisk [this message]
2008-08-29 20:45 ` Rationale for paccept() sigset argument? Michael Kerrisk
2008-09-02 0:48 ` Ulrich Drepper
2008-09-02 7:58 ` Michael Kerrisk
2008-09-08 13:33 ` Michael Kerrisk
2008-09-11 5:48 ` Michael Kerrisk
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