Re: [Qemu-devel] [PATCH] Handle G_IO_HUP in tcp_chr_read for tcp chardev

[Kirill Batuzov <batuzovk@ispras.ru>]

On Mon, 7 Jul 2014, Nikolay Nikolaev wrote:

> On Tue, Jul 1, 2014 at 2:52 PM, Kirill Batuzov <batuzovk@ispras.ru> wrote:
> > Due to GLib limitations it is not possible to create several watches on one
> > channel on Windows hosts. See bug #338943 in GNOME bugzilla for details:
> > https://bugzilla.gnome.org/show_bug.cgi?id=338943
> >
> > Handle G_IO_HUP in tcp_chr_read. It is already watched by corresponding watch.
> > Also remove the second watch with its handler.
> Shall this work when the connection is idle and the remote end closes it?
>

Yes, this should work. Why do you think it may not? The watch is
enabled, so tcp_chr_read will be called. During testing it handled
disconnects just fine.

> >
> > This reverts commit cdaa86a54b232572bba594bf87a7416e527e460c.
> > ("Add G_IO_HUP handler for socket chardev") but keeps its functionality.
> >
> > Cc: Antonios Motakis <a.motakis@virtualopensystems.com>
> > Cc: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>
> > Cc: Michael S. Tsirkin <mst@redhat.com>
> > Signed-off-by: Kirill Batuzov <batuzovk@ispras.ru>
> > Signed-off-by: Nikita Belov <zodiac@ispras.ru>
> > ---
> >
> > GLib limitation resulted in a bug on Windows host. Steps to reproduce:
> >
> > Start qemu: qemu-system-i386 -qmp tcp:127.0.0.1:4444:server:nowait
> > Connect with telnet: telnet 127.0.0.1 4444
> > Try sending some data from telnet.
> > Expected result: answers from QEMU.
> > Observed result: no answers (actually tcp_chr_read is not called at all).
> >
> > ---
> >  include/sysemu/char.h |    1 -
> >  qemu-char.c           |   27 ++++++---------------------
> >  2 files changed, 6 insertions(+), 22 deletions(-)
> >
> > diff --git a/include/sysemu/char.h b/include/sysemu/char.h
> > index c8b15f9..0bbd631 100644
> > --- a/include/sysemu/char.h
> > +++ b/include/sysemu/char.h
> > @@ -84,7 +84,6 @@ struct CharDriverState {
> >      int avail_connections;
> >      int is_mux;
> >      guint fd_in_tag;
> > -    guint fd_hup_tag;
> >      QemuOpts *opts;
> >      QTAILQ_ENTRY(CharDriverState) next;
> >  };
> > diff --git a/qemu-char.c b/qemu-char.c
> > index 51917de..22a9777 100644
> > --- a/qemu-char.c
> > +++ b/qemu-char.c
> > @@ -2673,6 +2673,12 @@ static gboolean tcp_chr_read(GIOChannel *chan, GIOCondition cond, void *opaque)
> >      uint8_t buf[READ_BUF_LEN];
> >      int len, size;
> >
> > +    if (cond & G_IO_HUP) {
> > +        /* connection closed */
> > +        tcp_chr_disconnect(chr);
> > +        return TRUE;
> > +    }
> > +
> >      if (!s->connected || s->max_size <= 0) {
> >          return TRUE;
> >      }
> > @@ -2724,25 +2730,6 @@ CharDriverState *qemu_chr_open_eventfd(int eventfd)
> >  }
> >  #endif
> >
> > -static gboolean tcp_chr_chan_close(GIOChannel *channel, GIOCondition cond,
> > -                                   void *opaque)
> > -{
> > -    CharDriverState *chr = opaque;
> > -
> > -    if (cond != G_IO_HUP) {
> > -        return FALSE;
> > -    }
> > -
> > -    /* connection closed */
> > -    tcp_chr_disconnect(chr);
> > -    if (chr->fd_hup_tag) {
> > -        g_source_remove(chr->fd_hup_tag);
> > -        chr->fd_hup_tag = 0;
> > -    }
> > -
> > -    return TRUE;
> > -}
> > -
> >  static void tcp_chr_connect(void *opaque)
> >  {
> >      CharDriverState *chr = opaque;
> > @@ -2752,8 +2739,6 @@ static void tcp_chr_connect(void *opaque)
> >      if (s->chan) {
> >          chr->fd_in_tag = io_add_watch_poll(s->chan, tcp_chr_read_poll,
> >                                             tcp_chr_read, chr);
> > -        chr->fd_hup_tag = g_io_add_watch(s->chan, G_IO_HUP, tcp_chr_chan_close,
> > -                                         chr);
> >      }
> >      qemu_chr_be_generic_open(chr);
> >  }
> > --
> > 1.7.10.4
> >
>