On Wed, 14 Feb 2018, Juergen Gross wrote:
> On 13/02/18 03:13, Stefano Stabellini wrote:
> > Introduce a per sock_mapping refcount, in addition to the existing
> > global refcount. Thanks to the sock_mapping refcount, we can safely wait
> > for it to be 1 in pvcalls_front_release before freeing an active socket,
> > instead of waiting for the global refcount to be 1.
> >
> > Signed-off-by: Stefano Stabellini
> >
> > ---
> > Changes in v2:
> > - fix code style
> > - nicer checks in pvcalls_front_release
> > - fix check in pvcalls_enter_sock
> > ---
> > drivers/xen/pvcalls-front.c | 193
> > +++-
> > 1 file changed, 81 insertions(+), 112 deletions(-)
> >
> > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> > index 4c789e6..163bf8c 100644
> > --- a/drivers/xen/pvcalls-front.c
> > +++ b/drivers/xen/pvcalls-front.c
> > @@ -60,6 +60,7 @@ struct sock_mapping {
> > bool active_socket;
> > struct list_head list;
> > struct socket *sock;
> > + atomic_t refcount;
> > union {
> > struct {
> > int irq;
> > @@ -93,6 +94,34 @@ struct sock_mapping {
> > };
> > };
> >
> > +static inline struct sock_mapping *pvcalls_enter_sock(struct socket *sock)
> > +{
> > + struct sock_mapping *map = NULL;
>
> Pointless initializer.
I'll fix
> > +
> > + if (!pvcalls_front_dev ||
> > + dev_get_drvdata(&pvcalls_front_dev->dev) == NULL)
> > + return ERR_PTR(-ENOTCONN);
> > +
> > + pvcalls_enter();
> > + map = (struct sock_mapping *)sock->sk->sk_send_head;
> > + if (map == NULL) {
> > + pvcalls_exit()
> > + return ERR_PTR(-ENOTSOCK);
> > + }
>
> Sorry for noticing this only now: any reason you don't call
> pvcalls_enter() only here instead? This would remove the need of
> calling pvcalls_exit() if map == NULL.
>
> I can't see pvcalls_enter() protecting sock->sk->sk_send_head in any
> way.
You are right. I'll move it down a couple of lines.
> > +
> > + atomic_inc(&map->refcount);
> > + return map;
> > +}
> > +
> > +static inline void pvcalls_exit_sock(struct socket *sock)
> > +{
> > + struct sock_mapping *map = NULL;
>
> Pointless initializer again.
I'll fix
