net: convert syn_wait_lock to a spinlock

This is a low hanging fruit, as we'll get rid of syn_wait_lock eventually.

We hold syn_wait_lock for such small sections, that it makes no sense to use
a read/write lock. A spin lock is simply faster.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 12 insertions, 12 deletions

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 711ab143d4cb..79c0c9439fdc 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -495,7 +495,7 @@ struct request_sock *inet_csk_search_req(struct sock *sk,
         u32 hash = inet_synq_hash(raddr, rport, lopt->hash_rnd,
                                   lopt->nr_table_entries);
 
-        write_lock(&icsk->icsk_accept_queue.syn_wait_lock);
+        spin_lock(&icsk->icsk_accept_queue.syn_wait_lock);
         for (req = lopt->syn_table[hash]; req != NULL; req = req->dl_next) {
                 const struct inet_request_sock *ireq = inet_rsk(req);
 
@@ -508,7 +508,7 @@ struct request_sock *inet_csk_search_req(struct sock *sk,
                         break;
                 }
         }
-        write_unlock(&icsk->icsk_accept_queue.syn_wait_lock);
+        spin_unlock(&icsk->icsk_accept_queue.syn_wait_lock);
 
         return req;
 }
@@ -650,10 +650,10 @@ void reqsk_queue_hash_req(struct request_sock_queue *queue,
         setup_timer(&req->rsk_timer, reqsk_timer_handler, (unsigned long)req);
         req->rsk_hash = hash;
 
-        write_lock(&queue->syn_wait_lock);
+        spin_lock(&queue->syn_wait_lock);
         req->dl_next = lopt->syn_table[hash];
         lopt->syn_table[hash] = req;
-        write_unlock(&queue->syn_wait_lock);
+        spin_unlock(&queue->syn_wait_lock);
 
         mod_timer_pinned(&req->rsk_timer, jiffies + timeout);
 }
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index f984b2001d0a..76322c9867d5 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -728,7 +728,7 @@ static int inet_diag_dump_reqs(struct sk_buff *skb, struct sock *sk,
 
         entry.family = sk->sk_family;
 
-        read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+        spin_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
 
         lopt = icsk->icsk_accept_queue.listen_opt;
         if (!lopt || !listen_sock_qlen(lopt))
@@ -776,7 +776,7 @@ static int inet_diag_dump_reqs(struct sk_buff *skb, struct sock *sk,
         }
 
 out:
-        read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+        spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
 
         return err;
 }
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 5554b8f33d41..8028ad5920a4 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1909,13 +1909,13 @@ get_req:
                 }
                 sk        = sk_nulls_next(st->syn_wait_sk);
                 st->state = TCP_SEQ_STATE_LISTENING;
-                read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+                spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
         } else {
                 icsk = inet_csk(sk);
-                read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+                spin_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
                 if (reqsk_queue_len(&icsk->icsk_accept_queue))
                         goto start_req;
-                read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+                spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
                 sk = sk_nulls_next(sk);
         }
 get_sk:
@@ -1927,7 +1927,7 @@ get_sk:
                         goto out;
                 }
                 icsk = inet_csk(sk);
-                read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+                spin_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
                 if (reqsk_queue_len(&icsk->icsk_accept_queue)) {
 start_req:
                         st->uid         = sock_i_uid(sk);
@@ -1936,7 +1936,7 @@ start_req:
                         st->sbucket     = 0;
                         goto get_req;
                 }
-                read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+                spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
         }
         spin_unlock_bh(&ilb->lock);
         st->offset = 0;
@@ -2155,7 +2155,7 @@ static void tcp_seq_stop(struct seq_file *seq, void *v)
         case TCP_SEQ_STATE_OPENREQ:
                 if (v) {
                         struct inet_connection_sock *icsk = inet_csk(st->syn_wait_sk);
-                        read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+                        spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
                 }
         case TCP_SEQ_STATE_LISTENING:
                 if (v != SEQ_START_TOKEN)