Re: [Qemu-devel] [PATCH] vhost-user: delay vhost_user_stop

["Marc-André Lureau" <mlureau@redhat.com>]

Hi

----- Original Message -----
> * Marc-André Lureau (marcandre.lureau@redhat.com) wrote:
> > Since commit b0a335e351103bf92f3f9d0bd5759311be8156ac, a socket write
> > may trigger a disconnect events, calling vhost_user_stop() and clearing
> > all the vhost_dev strutures holding data that vhost.c functions expect
> > to remain valid. Delay the cleanup to keep the vhost_dev structure
> > valid during the vhost.c functions.
> > 
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> This does get me through a 'make check' succesfully.
> 

Yes, it's not optimal, but there is so much cleanup to deal with otherwise, than I am inclined to go with this approach for now, and keep the FIXME for 2.10

I'll update the patch to avoid the race on reconnect.

> Dave
> 
> > ---
> >  net/vhost-user.c | 49 +++++++++++++++++++++++++++++++++++++++++++------
> >  1 file changed, 43 insertions(+), 6 deletions(-)
> > 
> > diff --git a/net/vhost-user.c b/net/vhost-user.c
> > index 77b8110f8c..00573c8ac8 100644
> > --- a/net/vhost-user.c
> > +++ b/net/vhost-user.c
> > @@ -25,6 +25,7 @@ typedef struct VhostUserState {
> >      guint watch;
> >      uint64_t acked_features;
> >      bool started;
> > +    QEMUBH *chr_closed_bh;
> >  } VhostUserState;
> >  
> >  VHostNetState *vhost_user_get_vhost_net(NetClientState *nc)
> > @@ -190,9 +191,40 @@ static gboolean net_vhost_user_watch(GIOChannel *chan,
> > GIOCondition cond,
> >  
> >      qemu_chr_fe_disconnect(&s->chr);
> >  
> > +    s->watch = 0;
> >      return FALSE;
> >  }
> >  
> > +static void chr_closed_bh(void *opaque)
> > +{
> > +    const char *name = opaque;
> > +    NetClientState *ncs[MAX_QUEUE_NUM];
> > +    VhostUserState *s;
> > +    Error *err = NULL;
> > +    int queues;
> > +
> > +    queues = qemu_find_net_clients_except(name, ncs,
> > +                                          NET_CLIENT_DRIVER_NIC,
> > +                                          MAX_QUEUE_NUM);
> > +    assert(queues < MAX_QUEUE_NUM);
> > +
> > +    s = DO_UPCAST(VhostUserState, nc, ncs[0]);
> > +
> > +    qmp_set_link(name, false, &err);
> > +    vhost_user_stop(queues, ncs);
> > +    if (s->watch) {
> > +        g_source_remove(s->watch);
> > +    }
> > +    s->watch = 0;
> > +
> > +    qemu_bh_delete(s->chr_closed_bh);
> > +    s->chr_closed_bh = NULL;
> > +
> > +    if (err) {
> > +        error_report_err(err);
> > +    }
> > +}
> > +
> >  static void net_vhost_user_event(void *opaque, int event)
> >  {
> >      const char *name = opaque;
> > @@ -212,20 +244,25 @@ static void net_vhost_user_event(void *opaque, int
> > event)
> >      trace_vhost_user_event(chr->label, event);
> >      switch (event) {
> >      case CHR_EVENT_OPENED:
> > -        s->watch = qemu_chr_fe_add_watch(&s->chr, G_IO_HUP,
> > -                                         net_vhost_user_watch, s);
> >          if (vhost_user_start(queues, ncs, &s->chr) < 0) {
> >              qemu_chr_fe_disconnect(&s->chr);
> >              return;
> >          }
> > +        s->watch = qemu_chr_fe_add_watch(&s->chr, G_IO_HUP,
> > +                                         net_vhost_user_watch, s);
> >          qmp_set_link(name, true, &err);
> > +        s->chr_closed_bh = qemu_bh_new(chr_closed_bh, opaque);
> >          s->started = true;
> >          break;
> >      case CHR_EVENT_CLOSED:
> > -        qmp_set_link(name, false, &err);
> > -        vhost_user_stop(queues, ncs);
> > -        g_source_remove(s->watch);
> > -        s->watch = 0;
> > +        /* a close event may happen during a read/write, but vhost
> > +         * code assumes the vhost_dev remains setup, so delay the
> > +         * stop & clear to idle.
> > +         * FIXME: better handle failure in vhost code, remove bh
> > +         */
> > +        if (s->chr_closed_bh) {
> > +            qemu_bh_schedule(s->chr_closed_bh);
> > +        }
> >          break;
> >      }
> >  
> > --
> > 2.12.0.rc2.3.gc93709801
> > 
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
>