net: convert TCP/DCCP ehash rwlocks to spinlocks

Now TCP & DCCP use RCU lookups, we can convert ehash rwlocks to spinlocks.

/proc/net/tcp and other seq_file 'readers' can safely be converted to 'writers'.

This should speedup writers, since spin_lock()/spin_unlock()
only use one atomic operation instead of two for write_lock()/write_unlock()

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 6 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 330b08a1227..a81caa1be0c 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1970,13 +1970,13 @@ static void *established_get_first(struct seq_file *seq)
                 struct sock *sk;
                 struct hlist_nulls_node *node;
                 struct inet_timewait_sock *tw;
-                rwlock_t *lock = inet_ehash_lockp(&tcp_hashinfo, st->bucket);
+                spinlock_t *lock = inet_ehash_lockp(&tcp_hashinfo, st->bucket);
 
                 /* Lockless fast path for the common case of empty buckets */
                 if (empty_bucket(st))
                         continue;
 
-                read_lock_bh(lock);
+                spin_lock_bh(lock);
                 sk_nulls_for_each(sk, node, &tcp_hashinfo.ehash[st->bucket].chain) {
                         if (sk->sk_family != st->family ||
                             !net_eq(sock_net(sk), net)) {
@@ -1995,7 +1995,7 @@ static void *established_get_first(struct seq_file *seq)
                         rc = tw;
                         goto out;
                 }
-                read_unlock_bh(lock);
+                spin_unlock_bh(lock);
                 st->state = TCP_SEQ_STATE_ESTABLISHED;
         }
 out:
@@ -2023,7 +2023,7 @@ get_tw:
                         cur = tw;
                         goto out;
                 }
-                read_unlock_bh(inet_ehash_lockp(&tcp_hashinfo, st->bucket));
+                spin_unlock_bh(inet_ehash_lockp(&tcp_hashinfo, st->bucket));
                 st->state = TCP_SEQ_STATE_ESTABLISHED;
 
                 /* Look for next non empty bucket */
@@ -2033,7 +2033,7 @@ get_tw:
                 if (st->bucket >= tcp_hashinfo.ehash_size)
                         return NULL;
 
-                read_lock_bh(inet_ehash_lockp(&tcp_hashinfo, st->bucket));
+                spin_lock_bh(inet_ehash_lockp(&tcp_hashinfo, st->bucket));
                 sk = sk_nulls_head(&tcp_hashinfo.ehash[st->bucket].chain);
         } else
                 sk = sk_nulls_next(sk);
@@ -2134,7 +2134,7 @@ static void tcp_seq_stop(struct seq_file *seq, void *v)
         case TCP_SEQ_STATE_TIME_WAIT:
         case TCP_SEQ_STATE_ESTABLISHED:
                 if (v)
-                        read_unlock_bh(inet_ehash_lockp(&tcp_hashinfo, st->bucket));
+                        spin_unlock_bh(inet_ehash_lockp(&tcp_hashinfo, st->bucket));
                 break;
         }
 }