From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ying Xue Subject: [PATCH net-next 2/3] netlink: eliminate nl_sk_hash_lock Date: Fri, 9 Jan 2015 16:23:37 +0800 Message-ID: <1420791818-22150-3-git-send-email-ying.xue@windriver.com> References: <1420791818-22150-1-git-send-email-ying.xue@windriver.com> Mime-Version: 1.0 Content-Type: text/plain Cc: , To: Return-path: Received: from mail1.windriver.com ([147.11.146.13]:32872 "EHLO mail1.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754085AbbAIIYI (ORCPT ); Fri, 9 Jan 2015 03:24:08 -0500 In-Reply-To: <1420791818-22150-1-git-send-email-ying.xue@windriver.com> Sender: netdev-owner@vger.kernel.org List-ID: As rhashtable_lookup_compare_insert() can guarantee the process of search and insertion is atomic, it's safe to eliminate the nl_sk_hash_lock. After this, object insertion or removal will be protected with per bucket lock on write side while object lookup is guarded with rcu read lock on read side. Signed-off-by: Ying Xue Cc: Thomas Graf --- net/netlink/af_netlink.c | 43 ++++++++++++++++++++++--------------------- net/netlink/af_netlink.h | 1 - net/netlink/diag.c | 10 +++++----- 3 files changed, 27 insertions(+), 27 deletions(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 298e1df..ac1daf3 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -98,7 +98,7 @@ static void netlink_skb_destructor(struct sk_buff *skb); /* nl_table locking explained: * Lookup and traversal are protected with an RCU read-side lock. Insertion - * and removal are protected with nl_sk_hash_lock while using RCU list + * and removal are protected with per bucket lock while using RCU list * modification primitives and may run in parallel to RCU protected lookups. * Destruction of the Netlink socket may only occur *after* nl_table_lock has * been acquired * either during or after the socket has been removed from @@ -110,10 +110,6 @@ static atomic_t nl_table_users = ATOMIC_INIT(0); #define nl_deref_protected(X) rcu_dereference_protected(X, lockdep_is_held(&nl_table_lock)); -/* Protects netlink socket hash table mutations */ -DEFINE_MUTEX(nl_sk_hash_lock); -EXPORT_SYMBOL_GPL(nl_sk_hash_lock); - static ATOMIC_NOTIFIER_HEAD(netlink_chain); static DEFINE_SPINLOCK(netlink_tap_lock); @@ -998,6 +994,19 @@ static struct sock *__netlink_lookup(struct netlink_table *table, u32 portid, &netlink_compare, &arg); } +static bool __netlink_insert(struct netlink_table *table, struct sock *sk, + struct net *net) +{ + struct netlink_compare_arg arg = { + .net = net, + .portid = nlk_sk(sk)->portid, + }; + + return rhashtable_lookup_compare_insert(&table->hash, + &nlk_sk(sk)->node, + &netlink_compare, &arg); +} + static struct sock *netlink_lookup(struct net *net, int protocol, u32 portid) { struct netlink_table *table = &nl_table[protocol]; @@ -1041,41 +1050,33 @@ netlink_update_listeners(struct sock *sk) static int netlink_insert(struct sock *sk, struct net *net, u32 portid) { struct netlink_table *table = &nl_table[sk->sk_protocol]; - int err = -EADDRINUSE; - - mutex_lock(&nl_sk_hash_lock); - if (__netlink_lookup(table, portid, net)) - goto err; - err = -EBUSY; if (nlk_sk(sk)->portid) - goto err; + return -EBUSY; - err = -ENOMEM; if (BITS_PER_LONG > 32 && unlikely(atomic_read(&table->hash.nelems) >= UINT_MAX)) - goto err; + return -ENOMEM; nlk_sk(sk)->portid = portid; sock_hold(sk); - rhashtable_insert(&table->hash, &nlk_sk(sk)->node); - err = 0; -err: - mutex_unlock(&nl_sk_hash_lock); - return err; + if (!__netlink_insert(table, sk, net)) { + sock_put(sk); + return -EADDRINUSE; + } + + return 0; } static void netlink_remove(struct sock *sk) { struct netlink_table *table; - mutex_lock(&nl_sk_hash_lock); table = &nl_table[sk->sk_protocol]; if (rhashtable_remove(&table->hash, &nlk_sk(sk)->node)) { WARN_ON(atomic_read(&sk->sk_refcnt) == 1); __sock_put(sk); } - mutex_unlock(&nl_sk_hash_lock); netlink_table_grab(); if (nlk_sk(sk)->subscriptions) { diff --git a/net/netlink/af_netlink.h b/net/netlink/af_netlink.h index fd96fa7..7518375 100644 --- a/net/netlink/af_netlink.h +++ b/net/netlink/af_netlink.h @@ -74,6 +74,5 @@ struct netlink_table { extern struct netlink_table *nl_table; extern rwlock_t nl_table_lock; -extern struct mutex nl_sk_hash_lock; #endif diff --git a/net/netlink/diag.c b/net/netlink/diag.c index fcca36d..bb59a7e 100644 --- a/net/netlink/diag.c +++ b/net/netlink/diag.c @@ -103,7 +103,7 @@ static int __netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb, { struct netlink_table *tbl = &nl_table[protocol]; struct rhashtable *ht = &tbl->hash; - const struct bucket_table *htbl = rht_dereference(ht->tbl, ht); + const struct bucket_table *htbl = rht_dereference_rcu(ht->tbl, ht); struct net *net = sock_net(skb->sk); struct netlink_diag_req *req; struct netlink_sock *nlsk; @@ -115,7 +115,7 @@ static int __netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb, for (i = 0; i < htbl->size; i++) { struct rhash_head *pos; - rht_for_each_entry(nlsk, pos, htbl, i, node) { + rht_for_each_entry_rcu(nlsk, pos, htbl, i, node) { sk = (struct sock *)nlsk; if (!net_eq(sock_net(sk), net)) @@ -172,7 +172,7 @@ static int netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb) req = nlmsg_data(cb->nlh); - mutex_lock(&nl_sk_hash_lock); + rcu_read_lock(); read_lock(&nl_table_lock); if (req->sdiag_protocol == NDIAG_PROTO_ALL) { @@ -186,7 +186,7 @@ static int netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb) } else { if (req->sdiag_protocol >= MAX_LINKS) { read_unlock(&nl_table_lock); - mutex_unlock(&nl_sk_hash_lock); + rcu_read_unlock(); return -ENOENT; } @@ -194,7 +194,7 @@ static int netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb) } read_unlock(&nl_table_lock); - mutex_unlock(&nl_sk_hash_lock); + rcu_read_unlock(); return skb->len; } -- 1.7.9.5