> From: Paolo Bonzini [mailto:[email protected]] On Behalf Of Paolo
> Bonzini
> Sent: Wednesday, September 05, 2012 5:26 PM
> To: Joachim Schmitz
> Cc: 'Junio C Hamano'; [email protected]; 'Erik Faye-Lund';
> [email protected]
> Subject: Re: poll() emulation in git
>
> Il 05/09/2012 15:36, Joachim Schmitz ha scritto:
> >>> > > Does your system have a working FIONREAD ioctl for pipes?
> >> >
> >> > It does have FIONREAD ioctl. Whether it works properly is to be
> >> > determined...
> >> > I'll test if you could show me how?
> > Oh, now I see what you aimed at, but no, that Mac OS X method doesn't work
> > for me, I tried (at least I think I did).
> >
> > And <sys/ioctl.h> has
> > /*
> > * Normal IOCTL's supported by the socket interface
> > */
> > #define FIONREAD _IOR(0, 8, _ioctl_int) /* Num of bytes to
> > read */
> > #define FIONBIO _IOW(0, 9, _ioctl_int) /* Non-blocking I/O
> > */
> >
> > So these seem to be supported on sockets only, I guess.
> > And indeed the man pages for ioctl confirms:
> >
> > Valid values for the request parameter for AF_INET or
> > AF_INET6 sockets are:
> >
> >
> > FIONREAD Gets the number of bytes available for reading and
> > stores it at the int pointed at by arg.
> >
> >
> > So not even AF_UNIX sockets, not to mention pipes...
>
> So there's no way you can support POLLHUP. Your system is quite
> crippled. :(
Unfortunatly.
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.
In daemon.c it seems to be all sockets it polls on, so it should work on
NonStop.
Same in credential-cache--daemon.c
Remains upload-pack.c and builtin/upload-archive.c
In both start_command() gathers the FDs to poll() on and that indeed works on
pipes -> problem on NonStop!
Seeing that in those cases xread() takes care of EAGAIN, I've now used 'brute
force' in poll.c:
...
# 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?
Bye, Jojo
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