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RE: poll() emulation in git
From: |
Joachim Schmitz |
Subject: |
RE: poll() emulation in git |
Date: |
Thu, 6 Sep 2012 16:44:39 +0200 |
> From: Paolo Bonzini [mailto:address@hidden On Behalf Of Paolo Bonzini
> Sent: Thursday, September 06, 2012 4:32 PM
> To: Joachim Schmitz
> Cc: address@hidden; 'Junio C Hamano'; 'Erik Faye-Lund'; address@hidden;
> address@hidden
> Subject: Re: poll() emulation in git
>
> Il 06/09/2012 16:02, Joachim Schmitz ha scritto:
> >
> > But is there something that could be done to make git work even without
> > poll()?
> > It is used in 5 places:
> >
> > $ grep -n poll\( *.c */*.c
> > credential-cache--daemon.c:175: if (poll(&pfd, 1, 1000 * wakeup) < 0) {
> > daemon.c:1018: if (poll(pfd, socklist->nr, -1) < 0) {
> > help.c:361: poll(NULL, 0, autocorrect * 100);
> > upload-pack.c:232: if (poll(pfd, pollsize, -1) < 0) {
> > builtin/upload-archive.c:125: if (poll(pfd, 2, -1) < 0) {
> >
> > Don't quite understand why in help.c it has that NULL, which should always
> > result in an EFAULT and other than that basically is
a
> > NOP (at least in the poll() emulation)? Seems a usleep(autocorrect * 100)
> > is meant to happen here instead?
> > So I think here a poll() isn't needed at all. But also the 'broken' one
> > shouldn't harm too much.
>
> Yes, it's an usleep(autocorrect * 100000) basically (poll takes
> milliseconds, not micro).
OK, it is _supposed_ to do this usleep(), but is does not, as poll() returns
early with EFAULT in this case:
/* EFAULT is not necessary to implement, but let's do it in the
simplest case. */
if (!pfd)
{
errno = EFAULT;
return -1;
}
poll() is doing this before calling select(), so won't sleep.
So there's a bug in {gnulib|git}'s poll(), right?
> > ...
> > # else
> > char data[64];
> > r = recv (fd, data, sizeof (data), MSG_PEEK);
> > socket_errno = (r < 0) ? errno : 0;
> > # endif
> > if (r == 0)
> > happened |= POLLHUP;
> >
> > /* If the event happened on an unconnected server socket,
> > that's fine. */
> > else if (r > 0 || ( /* (r == -1) && */ socket_errno == ENOTCONN))
> > happened |= (POLLIN | POLLRDNORM) & sought;
> >
> > /* Distinguish hung-up sockets from other errors. */
> > else if (socket_errno == ESHUTDOWN || socket_errno == ECONNRESET
> > || socket_errno == ECONNABORTED || socket_errno == ENETRESET)
> > happened |= POLLHUP;
> >
> > #ifdef __TANDEM /* as we can't recv(...,MSG_PEEK) on a non-socket */
> > else if (socket_errno == ENOTSOCK)
> > happened |= (POLLIN | POLLRDNORM) & sought;
> > #endif
> > else
> > happened |= POLLERR;
> > }
> > ...
> >
> > We won't detect POLLHUP that way I think. However it seems to work, we've
> > been able to clone, push, pull, branch that way with
> > NonStop being the (ssh-)server, something that didn't work at all without
> > that hack (and yes, I believe it is just that).
> > Someone in for a cleaner way of managing this?
>
> I suppose it works to always handle ENOTSOCK that way, even on
> non-__TANDEM systems.
So you think this is a clean way of dealing with it?
Bye, Jojo
- RE: poll() emulation in git, Joachim Schmitz, 2012/09/05
- Re: poll() emulation in git, Bastien ROUCARIES, 2012/09/05
- Re: poll() emulation in git, Paolo Bonzini, 2012/09/05
- RE: poll() emulation in git, Joachim Schmitz, 2012/09/05
- RE: poll() emulation in git, Joachim Schmitz, 2012/09/05
- Re: poll() emulation in git, Paolo Bonzini, 2012/09/05
- RE: poll() emulation in git, Joachim Schmitz, 2012/09/06
- Re: poll() emulation in git, Paolo Bonzini, 2012/09/06
- RE: poll() emulation in git,
Joachim Schmitz <=
- Re: poll() emulation in git, Paolo Bonzini, 2012/09/06
- RE: poll() emulation in git, Joachim Schmitz, 2012/09/07
- RE: poll() emulation in git, Joachim Schmitz, 2012/09/07
- Re: poll() emulation in git, Paolo Bonzini, 2012/09/07