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, 11 insertions, 11 deletions

diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 60689951ecdb..8554d0ea1719 100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -20,16 +20,16 @@ static void __inet_twsk_kill(struct inet_timewait_sock *tw,
         struct inet_bind_hashbucket *bhead;
         struct inet_bind_bucket *tb;
         /* Unlink from established hashes. */
-        rwlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
+        spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
 
-        write_lock(lock);
+        spin_lock(lock);
         if (hlist_nulls_unhashed(&tw->tw_node)) {
-                write_unlock(lock);
+                spin_unlock(lock);
                 return;
         }
         hlist_nulls_del_rcu(&tw->tw_node);
         sk_nulls_node_init(&tw->tw_node);
-        write_unlock(lock);
+        spin_unlock(lock);
 
         /* Disassociate with bind bucket. */
         bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
@@ -76,7 +76,7 @@ void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
         const struct inet_sock *inet = inet_sk(sk);
         const struct inet_connection_sock *icsk = inet_csk(sk);
         struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
-        rwlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
+        spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
         struct inet_bind_hashbucket *bhead;
         /* Step 1: Put TW into bind hash. Original socket stays there too.
            Note, that any socket with inet->num != 0 MUST be bound in
@@ -90,7 +90,7 @@ void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
         inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
         spin_unlock(&bhead->lock);
 
-        write_lock(lock);
+        spin_lock(lock);
 
         /*
          * Step 2: Hash TW into TIMEWAIT chain.
@@ -104,7 +104,7 @@ void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
         if (__sk_nulls_del_node_init_rcu(sk))
                 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
 
-        write_unlock(lock);
+        spin_unlock(lock);
 }
 
 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
@@ -427,9 +427,9 @@ void inet_twsk_purge(struct net *net, struct inet_hashinfo *hashinfo,
         for (h = 0; h < (hashinfo->ehash_size); h++) {
                 struct inet_ehash_bucket *head =
                         inet_ehash_bucket(hashinfo, h);
-                rwlock_t *lock = inet_ehash_lockp(hashinfo, h);
+                spinlock_t *lock = inet_ehash_lockp(hashinfo, h);
 restart:
-                write_lock(lock);
+                spin_lock(lock);
                 sk_nulls_for_each(sk, node, &head->twchain) {
 
                         tw = inet_twsk(sk);
@@ -438,13 +438,13 @@ restart:
                                 continue;
 
                         atomic_inc(&tw->tw_refcnt);
-                        write_unlock(lock);
+                        spin_unlock(lock);
                         inet_twsk_deschedule(tw, twdr);
                         inet_twsk_put(tw);
 
                         goto restart;
                 }
-                write_unlock(lock);
+                spin_unlock(lock);
         }
         local_bh_enable();
 }