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

[Nikolay Nikolaev]

On Tue, Jul 1, 2014 at 2:52 PM, Kirill Batuzov <address@hidden> 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?

>
> This reverts commit cdaa86a54b232572bba594bf87a7416e527e460c.
> ("Add G_IO_HUP handler for socket chardev") but keeps its functionality.
>
> Cc: Antonios Motakis <address@hidden>
> Cc: Nikolay Nikolaev <address@hidden>
> Cc: Michael S. Tsirkin <address@hidden>
> Signed-off-by: Kirill Batuzov <address@hidden>
> Signed-off-by: Nikita Belov <address@hidden>
> ---
>
> 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
>