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SubjectRe: paccept() oddity
On Wed, 20 Aug 2008 18:50:54 +0200 Michael Kerrisk <mtk.manpages@googlemail.com> wrote:

> Ulrich,
>
> [
> 2.6.27-rc has paccept():
>
> int paccept(int fd, struct sockaddr *sockaddr, socklen_t *addrlen,
> const sigset_t *sigmask, int setsize, int flags)
> ]
>
> While considering the sigset argument for paccept() (see my previous
> message), and testing that system call, I realized that there is a certain
> oddness in the implementation of paccept().
>
> Like accept(), paccept() automatically restarts if interrupted by a signal
> handler that was established with the SA_RESTART flag.
>
> On the other hand, pselect(), ppoll(), and epoll_pwait() are never restarted
> if interrupted by a handler, even if the handler was established with
> SA_RESTART. (This is the same as with select(), poll(), and epoll_wait().)
>
> It seems to me that it makes little sense to restart paccept(), especially in
> the case where it is interrupted by a handler for one of the signals that is
> in sigmask, since the whole point of calling paccept() is to block until a
> connection is received, or until one of the signals in sigmask is caught().
>
> How about changing paccept() so that it is never automatically restarted if
> interrupted by a signal handler, regardless of the SA_RESTART flag. (In
> other words, paccept() should be consistent with pselect(), ppoll(), and
> epoll_pwait(), rather than being consistent with accept().) What are your
> thoughts?
>

Oleg, Roland: would you have the time to ponder the above, please?

If we can't get this nailed down very soon I'd suggest that we disable
sys_paccept() for 2.6.27. We don't want to be releasing a new system
call into 2.6.27 if there are doubts surrounding its userspace-visible
behaviour.

Thanks.


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