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)