Re: [Xen-devel] [PATCH 1/2] pvcalls-front: introduce a per sock_mapping refcount

[Stefano Stabellini]

On Mon, 12 Feb 2018, Juergen Gross wrote:
> On 05/02/18 23:51, 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 
> > ---
> >  drivers/xen/pvcalls-front.c | 190 
> > ++--
> >  1 file changed, 78 insertions(+), 112 deletions(-)
> > 
> > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> > index 4c789e6..164d3ad 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 +94,33 @@ struct sock_mapping {
> > };
> >  };
> >  
> > +static inline struct sock_mapping *pvcalls_enter_sock(struct socket *sock)
> > +{
> > +   struct sock_mapping *map = NULL;
> > +
> > +   if (!pvcalls_front_dev || _front_dev->dev == NULL)
> 
> Did you mean:
> if (!pvcalls_front_dev || !pvcalls_front_dev->dev)

I actually meant:

if (!pvcalls_front_dev || dev_get_drvdata(_front_dev->dev) == NULL)

 
> > +   return ERR_PTR(-ENOTCONN);
> > +
> > +   pvcalls_enter();
> > +   map = (struct sock_mapping *) sock->sk->sk_send_head;
> 
> Style: no blank after the cast, please (multiple times).

OK, I'll fix them all


> > +   if (map == NULL) {
> > +   pvcalls_exit()
> > +   return ERR_PTR(-ENOTSOCK);
> > +   }
> > +
> > +   atomic_inc(>refcount);
> > +   return map;
> > +}
> > +
> > +static inline void pvcalls_exit_sock(struct socket *sock)
> > +{
> > +   struct sock_mapping *map = NULL;
> > +
> > +   map = (struct sock_mapping *) sock->sk->sk_send_head;
> > +   atomic_dec(>refcount);
> > +   pvcalls_exit();
> > +}
> > +
> >  static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
> >  {
> > *req_id = bedata->ring.req_prod_pvt & (RING_SIZE(>ring) - 1);
> > @@ -369,31 +397,23 @@ int pvcalls_front_connect(struct socket *sock, struct 
> > sockaddr *addr,
> > if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
> > return -EOPNOTSUPP;
> >  
> > -   pvcalls_enter();
> > -   if (!pvcalls_front_dev) {
> > -   pvcalls_exit();
> > -   return -ENOTCONN;
> > -   }
> > +   map = pvcalls_enter_sock(sock);
> > +   if (IS_ERR(map))
> > +   return PTR_ERR(map);
> >  
> > bedata = dev_get_drvdata(_front_dev->dev);
> >  
> > -   map = (struct sock_mapping *)sock->sk->sk_send_head;
> > -   if (!map) {
> > -   pvcalls_exit();
> > -   return -ENOTSOCK;
> > -   }
> > -
> > spin_lock(>socket_lock);
> > ret = get_request(bedata, _id);
> > if (ret < 0) {
> > spin_unlock(>socket_lock);
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> > return ret;
> > }
> > ret = create_active(map, );
> > if (ret < 0) {
> > spin_unlock(>socket_lock);
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> > return ret;
> > }
> >  
> > @@ -423,7 +443,7 @@ int pvcalls_front_connect(struct socket *sock, struct 
> > sockaddr *addr,
> > smp_rmb();
> > ret = bedata->rsp[req_id].ret;
> > bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> > return ret;
> >  }
> >  
> > @@ -488,23 +508,15 @@ int pvcalls_front_sendmsg(struct socket *sock, struct 
> > msghdr *msg,
> > if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
> > return -EOPNOTSUPP;
> >  
> > -   pvcalls_enter();
> > -   if (!pvcalls_front_dev) {
> > -   pvcalls_exit();
> > -   return -ENOTCONN;
> > -   }
> > +   map = pvcalls_enter_sock(sock);
> > +   if (IS_ERR(map))
> > +   return PTR_ERR(map);
> > bedata = dev_get_drvdata(_front_dev->dev);
> >  
> > -   map = (struct sock_mapping *) sock->sk->sk_send_head;
> > -   if (!map) {
> > -   pvcalls_exit();
> > -   return -ENOTSOCK;
> > -   }
> > -
> > mutex_lock(>active.out_mutex);
> > if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
> > mutex_unlock(>active.out_mutex);
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> > return -EAGAIN;
> > }
> > if (len > INT_MAX)
> > @@ -526,7 +538,7 @@ int pvcalls_front_sendmsg(struct socket *sock, struct 
> > msghdr *msg,
> > tot_sent = sent;
> >  
> > mutex_unlock(>active.out_mutex);
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> > return tot_sent;
> >  }
> >  
> > @@ -591,19 +603,11 @@ int pvcalls_front_recvmsg(struct 

Re: [Xen-devel] [PATCH 1/2] pvcalls-front: introduce a per sock_mapping refcount

[Juergen Gross]

On 05/02/18 23:51, 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 
> ---
>  drivers/xen/pvcalls-front.c | 190 
> ++--
>  1 file changed, 78 insertions(+), 112 deletions(-)
> 
> diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> index 4c789e6..164d3ad 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 +94,33 @@ struct sock_mapping {
>   };
>  };
>  
> +static inline struct sock_mapping *pvcalls_enter_sock(struct socket *sock)
> +{
> + struct sock_mapping *map = NULL;
> +
> + if (!pvcalls_front_dev || _front_dev->dev == NULL)

Did you mean:
if (!pvcalls_front_dev || !pvcalls_front_dev->dev)

> + return ERR_PTR(-ENOTCONN);
> +
> + pvcalls_enter();
> + map = (struct sock_mapping *) sock->sk->sk_send_head;

Style: no blank after the cast, please (multiple times).

> + if (map == NULL) {
> + pvcalls_exit()
> + return ERR_PTR(-ENOTSOCK);
> + }
> +
> + atomic_inc(>refcount);
> + return map;
> +}
> +
> +static inline void pvcalls_exit_sock(struct socket *sock)
> +{
> + struct sock_mapping *map = NULL;
> +
> + map = (struct sock_mapping *) sock->sk->sk_send_head;
> + atomic_dec(>refcount);
> + pvcalls_exit();
> +}
> +
>  static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
>  {
>   *req_id = bedata->ring.req_prod_pvt & (RING_SIZE(>ring) - 1);
> @@ -369,31 +397,23 @@ int pvcalls_front_connect(struct socket *sock, struct 
> sockaddr *addr,
>   if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
>   return -EOPNOTSUPP;
>  
> - pvcalls_enter();
> - if (!pvcalls_front_dev) {
> - pvcalls_exit();
> - return -ENOTCONN;
> - }
> + map = pvcalls_enter_sock(sock);
> + if (IS_ERR(map))
> + return PTR_ERR(map);
>  
>   bedata = dev_get_drvdata(_front_dev->dev);
>  
> - map = (struct sock_mapping *)sock->sk->sk_send_head;
> - if (!map) {
> - pvcalls_exit();
> - return -ENOTSOCK;
> - }
> -
>   spin_lock(>socket_lock);
>   ret = get_request(bedata, _id);
>   if (ret < 0) {
>   spin_unlock(>socket_lock);
> - pvcalls_exit();
> + pvcalls_exit_sock(sock);
>   return ret;
>   }
>   ret = create_active(map, );
>   if (ret < 0) {
>   spin_unlock(>socket_lock);
> - pvcalls_exit();
> + pvcalls_exit_sock(sock);
>   return ret;
>   }
>  
> @@ -423,7 +443,7 @@ int pvcalls_front_connect(struct socket *sock, struct 
> sockaddr *addr,
>   smp_rmb();
>   ret = bedata->rsp[req_id].ret;
>   bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
> - pvcalls_exit();
> + pvcalls_exit_sock(sock);
>   return ret;
>  }
>  
> @@ -488,23 +508,15 @@ int pvcalls_front_sendmsg(struct socket *sock, struct 
> msghdr *msg,
>   if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
>   return -EOPNOTSUPP;
>  
> - pvcalls_enter();
> - if (!pvcalls_front_dev) {
> - pvcalls_exit();
> - return -ENOTCONN;
> - }
> + map = pvcalls_enter_sock(sock);
> + if (IS_ERR(map))
> + return PTR_ERR(map);
>   bedata = dev_get_drvdata(_front_dev->dev);
>  
> - map = (struct sock_mapping *) sock->sk->sk_send_head;
> - if (!map) {
> - pvcalls_exit();
> - return -ENOTSOCK;
> - }
> -
>   mutex_lock(>active.out_mutex);
>   if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
>   mutex_unlock(>active.out_mutex);
> - pvcalls_exit();
> + pvcalls_exit_sock(sock);
>   return -EAGAIN;
>   }
>   if (len > INT_MAX)
> @@ -526,7 +538,7 @@ int pvcalls_front_sendmsg(struct socket *sock, struct 
> msghdr *msg,
>   tot_sent = sent;
>  
>   mutex_unlock(>active.out_mutex);
> - pvcalls_exit();
> + pvcalls_exit_sock(sock);
>   return tot_sent;
>  }
>  
> @@ -591,19 +603,11 @@ int pvcalls_front_recvmsg(struct socket *sock, struct 
> msghdr *msg, size_t len,
>   if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
>   return -EOPNOTSUPP;
>  
> - pvcalls_enter();
> - if (!pvcalls_front_dev) {
> - pvcalls_exit();
> - return