Phonet: use atomic for packet TX window

GPRS TX flow control won't need to lock the underlying socket anymore.

Signed-off-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 23 insertions, 19 deletions

diff --git a/include/net/phonet/pep.h b/include/net/phonet/pep.h
index fcd793030e4d..4c61cdce4e5f 100644
--- a/include/net/phonet/pep.h
+++ b/include/net/phonet/pep.h
@@ -35,12 +35,12 @@ struct pep_sock {
         struct sock             *listener;
         struct sk_buff_head     ctrlreq_queue;
 #define PNPIPE_CTRLREQ_MAX      10
+        atomic_t                tx_credits;
         int                     ifindex;
         u16                     peer_type;      /* peer type/subtype */
         u8                      pipe_handle;
 
         u8                      rx_credits;
-        u8                      tx_credits;
         u8                      rx_fc;  /* RX flow control */
         u8                      tx_fc;  /* TX flow control */
         u8                      init_enable;    /* auto-enable at creation */
diff --git a/net/phonet/pep.c b/net/phonet/pep.c
index bc6d50f83249..bb3e67849b38 100644
--- a/net/phonet/pep.c
+++ b/net/phonet/pep.c
@@ -225,6 +225,7 @@ static int pipe_rcv_status(struct sock *sk, struct sk_buff *skb)
 {
         struct pep_sock *pn = pep_sk(sk);
         struct pnpipehdr *hdr = pnp_hdr(skb);
+        int wake = 0;
 
         if (!pskb_may_pull(skb, sizeof(*hdr) + 4))
                 return -EINVAL;
@@ -241,16 +242,16 @@ static int pipe_rcv_status(struct sock *sk, struct sk_buff *skb)
                 case PN_LEGACY_FLOW_CONTROL:
                         switch (hdr->data[4]) {
                         case PEP_IND_BUSY:
-                                pn->tx_credits = 0;
+                                atomic_set(&pn->tx_credits, 0);
                                 break;
                         case PEP_IND_READY:
-                                pn->tx_credits = 1;
+                                atomic_set(&pn->tx_credits, wake = 1);
                                 break;
                         }
                         break;
                 case PN_ONE_CREDIT_FLOW_CONTROL:
                         if (hdr->data[4] == PEP_IND_READY)
-                                pn->tx_credits = 1;
+                                atomic_set(&pn->tx_credits, wake = 1);
                         break;
                 }
                 break;
@@ -258,10 +259,7 @@ static int pipe_rcv_status(struct sock *sk, struct sk_buff *skb)
         case PN_PEP_IND_ID_MCFC_GRANT_CREDITS:
                 if (pn->tx_fc != PN_MULTI_CREDIT_FLOW_CONTROL)
                         break;
-                if (pn->tx_credits + hdr->data[4] > 0xff)
-                        pn->tx_credits = 0xff;
-                else
-                        pn->tx_credits += hdr->data[4];
+                atomic_add(wake = hdr->data[4], &pn->tx_credits);
                 break;
 
         default:
@@ -269,7 +267,7 @@ static int pipe_rcv_status(struct sock *sk, struct sk_buff *skb)
                                 (unsigned)hdr->data[1]);
                 return -EOPNOTSUPP;
         }
-        if (pn->tx_credits)
+        if (wake)
                 sk->sk_write_space(sk);
         return 0;
 }
@@ -343,7 +341,7 @@ static int pipe_do_rcv(struct sock *sk, struct sk_buff *skb)
                 }
                 /* fall through */
         case PNS_PEP_DISABLE_REQ:
-                pn->tx_credits = 0;
+                atomic_set(&pn->tx_credits, 0);
                 pep_reply(sk, skb, PN_PIPE_NO_ERROR, NULL, 0, GFP_ATOMIC);
                 break;
 
@@ -390,7 +388,7 @@ static int pipe_do_rcv(struct sock *sk, struct sk_buff *skb)
                 /* fall through */
         case PNS_PIPE_ENABLED_IND:
                 if (!pn_flow_safe(pn->tx_fc)) {
-                        pn->tx_credits = 1;
+                        atomic_set(&pn->tx_credits, 1);
                         sk->sk_write_space(sk);
                 }
                 if (sk->sk_state == TCP_ESTABLISHED)
@@ -504,8 +502,9 @@ static int pep_connreq_rcv(struct sock *sk, struct sk_buff *skb)
         newpn->pn_sk.resource = pn->pn_sk.resource;
         skb_queue_head_init(&newpn->ctrlreq_queue);
         newpn->pipe_handle = pipe_handle;
+        atomic_set(&newpn->tx_credits, 0);
         newpn->peer_type = peer_type;
-        newpn->rx_credits = newpn->tx_credits = 0;
+        newpn->rx_credits = 0;
         newpn->rx_fc = newpn->tx_fc = PN_LEGACY_FLOW_CONTROL;
         newpn->init_enable = enabled;
 
@@ -821,14 +820,18 @@ static int pipe_skb_send(struct sock *sk, struct sk_buff *skb)
         struct pep_sock *pn = pep_sk(sk);
         struct pnpipehdr *ph;
 
+        if (pn_flow_safe(pn->tx_fc) &&
+            !atomic_add_unless(&pn->tx_credits, -1, 0)) {
+                kfree_skb(skb);
+                return -ENOBUFS;
+        }
+
         skb_push(skb, 3);
         skb_reset_transport_header(skb);
         ph = pnp_hdr(skb);
         ph->utid = 0;
         ph->message_id = PNS_PIPE_DATA;
         ph->pipe_handle = pn->pipe_handle;
-        if (pn_flow_safe(pn->tx_fc) && pn->tx_credits)
-                pn->tx_credits--;
 
         return pn_skb_send(sk, skb, &pipe_srv);
 }
@@ -866,7 +869,7 @@ disabled:
         BUG_ON(sk->sk_state != TCP_ESTABLISHED);
 
         /* Wait until flow control allows TX */
-        done = pn->tx_credits > 0;
+        done = atomic_read(&pn->tx_credits);
         while (!done) {
                 DEFINE_WAIT(wait);
 
@@ -881,7 +884,7 @@ disabled:
 
                 prepare_to_wait(&sk->sk_socket->wait, &wait,
                                 TASK_INTERRUPTIBLE);
-                done = sk_wait_event(sk, &timeo, pn->tx_credits > 0);
+                done = sk_wait_event(sk, &timeo, atomic_read(&pn->tx_credits));
                 finish_wait(&sk->sk_socket->wait, &wait);
 
                 if (sk->sk_state != TCP_ESTABLISHED)
@@ -895,7 +898,8 @@ disabled:
                         goto out;
                 skb_reserve(skb, MAX_PHONET_HEADER + 3);
 
-                if (sk->sk_state != TCP_ESTABLISHED || !pn->tx_credits)
+                if (sk->sk_state != TCP_ESTABLISHED ||
+                    !atomic_read(&pn->tx_credits))
                         goto disabled; /* sock_alloc_send_skb might sleep */
         }
 
@@ -917,7 +921,7 @@ int pep_writeable(struct sock *sk)
 {
         struct pep_sock *pn = pep_sk(sk);
 
-        return (sk->sk_state == TCP_ESTABLISHED) ? pn->tx_credits : 0;
+        return atomic_read(&pn->tx_credits);
 }
 
 int pep_write(struct sock *sk, struct sk_buff *skb)
diff --git a/net/phonet/socket.c b/net/phonet/socket.c
index c75aa5cdead5..ada2a35bf7a2 100644
--- a/net/phonet/socket.c
+++ b/net/phonet/socket.c
@@ -227,7 +227,7 @@ static unsigned int pn_socket_poll(struct file *file, struct socket *sock,
         if (!mask && sk->sk_state == TCP_CLOSE_WAIT)
                 return POLLHUP;
 
-        if (sk->sk_state == TCP_ESTABLISHED && pn->tx_credits)
+        if (sk->sk_state == TCP_ESTABLISHED && atomic_read(&pn->tx_credits))
                 mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
 
         return mask;