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Re: [Qemu-devel] [PATCH] vhost-user: Add ability to know vhost-user back


From: Nikolay Nikolaev
Subject: Re: [Qemu-devel] [PATCH] vhost-user: Add ability to know vhost-user backend disconnection
Date: Tue, 21 Apr 2015 23:19:43 +0300

On Tue, Apr 21, 2015 at 9:36 AM, Tetsuya Mukawa <address@hidden> wrote:
> Current QEMU cannot detect vhost-user backend disconnection. The
> patch adds ability to know it.
> To know disconnection, add watcher to detect G_IO_HUP event. When
> G_IO_HUP event is detected, the disconnected socket will be read
> to cause a CHR_EVENT_CLOSED.
>
> Signed-off-by: Tetsuya Mukawa <address@hidden>
> ---
>  net/vhost-user.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/net/vhost-user.c b/net/vhost-user.c
> index 1d86a2b..55c05a5 100644
> --- a/net/vhost-user.c
> +++ b/net/vhost-user.c
> @@ -19,6 +19,7 @@ typedef struct VhostUserState {
>      NetClientState nc;
>      CharDriverState *chr;
>      VHostNetState *vhost_net;
> +    int watch;
>  } VhostUserState;
>
>  typedef struct VhostUserChardevProps {
> @@ -113,12 +114,23 @@ static void net_vhost_link_down(VhostUserState *s, bool 
> link_down)
>      }
>  }
>
> +static gboolean net_vhost_user_watch(GIOChannel *chan, GIOCondition cond,
> +                                           void *opaque)
> +{
> +    VhostUserState *s = opaque;
> +    uint8_t buf[1];
> +
> +    qemu_chr_fe_read_all(s->chr, buf, sizeof(buf));
So you read the date from the buffer and just discard it?
Are you going to miss messages this way?

Please clarify.

regards,
Nikolay Nikolaev

> +    return FALSE;
> +}
> +
>  static void net_vhost_user_event(void *opaque, int event)
>  {
>      VhostUserState *s = opaque;
>
>      switch (event) {
>      case CHR_EVENT_OPENED:
> +        s->watch = qemu_chr_fe_add_watch(s->chr, G_IO_HUP, 
> net_vhost_user_watch, s);
>          vhost_user_start(s);
>          net_vhost_link_down(s, false);
>          error_report("chardev \"%s\" went up", s->chr->label);
> @@ -126,6 +138,8 @@ static void net_vhost_user_event(void *opaque, int event)
>      case CHR_EVENT_CLOSED:
>          net_vhost_link_down(s, true);
>          vhost_user_stop(s);
> +        g_source_remove(s->watch);
> +        s->watch = 0;
>          error_report("chardev \"%s\" went down", s->chr->label);
>          break;
>      }
> --
> 1.9.1
>
>



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