tcp: md5: remove spinlock usage in fast path

[pandora-kernel.git] / net / ipv4 / tcp.c

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ec8b4b7..573d786 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2863,9 +2863,8 @@ int tcp_gro_complete(struct sk_buff *skb)
 EXPORT_SYMBOL(tcp_gro_complete);
 
 #ifdef CONFIG_TCP_MD5SIG
-static unsigned long tcp_md5sig_users;
-static struct tcp_md5sig_pool __percpu *tcp_md5sig_pool;
-static DEFINE_SPINLOCK(tcp_md5sig_pool_lock);
+static struct tcp_md5sig_pool __percpu *tcp_md5sig_pool __read_mostly;
+static DEFINE_MUTEX(tcp_md5sig_mutex);
 
 static void __tcp_free_md5sig_pool(struct tcp_md5sig_pool __percpu *pool)
 {
@@ -2880,30 +2879,14 @@ static void __tcp_free_md5sig_pool(struct tcp_md5sig_pool __percpu *pool)
        free_percpu(pool);
 }
 
-void tcp_free_md5sig_pool(void)
-{
-       struct tcp_md5sig_pool __percpu *pool = NULL;
-
-       spin_lock_bh(&tcp_md5sig_pool_lock);
-       if (--tcp_md5sig_users == 0) {
-               pool = tcp_md5sig_pool;
-               tcp_md5sig_pool = NULL;
-       }
-       spin_unlock_bh(&tcp_md5sig_pool_lock);
-       if (pool)
-               __tcp_free_md5sig_pool(pool);
-}
-EXPORT_SYMBOL(tcp_free_md5sig_pool);
-
-static struct tcp_md5sig_pool __percpu *
-__tcp_alloc_md5sig_pool(struct sock *sk)
+static void __tcp_alloc_md5sig_pool(void)
 {
        int cpu;
        struct tcp_md5sig_pool __percpu *pool;
 
        pool = alloc_percpu(struct tcp_md5sig_pool);
        if (!pool)
-               return NULL;
+               return;
 
        for_each_possible_cpu(cpu) {
                struct crypto_hash *hash;
@@ -2914,53 +2897,27 @@ __tcp_alloc_md5sig_pool(struct sock *sk)
 
                per_cpu_ptr(pool, cpu)->md5_desc.tfm = hash;
        }
-       return pool;
+       /* before setting tcp_md5sig_pool, we must commit all writes
+        * to memory. See ACCESS_ONCE() in tcp_get_md5sig_pool()
+        */
+       smp_wmb();
+       tcp_md5sig_pool = pool;
+       return;
 out_free:
        __tcp_free_md5sig_pool(pool);
-       return NULL;
 }
 
-struct tcp_md5sig_pool __percpu *tcp_alloc_md5sig_pool(struct sock *sk)
+bool tcp_alloc_md5sig_pool(void)
 {
-       struct tcp_md5sig_pool __percpu *pool;
-       int alloc = 0;
-
-retry:
-       spin_lock_bh(&tcp_md5sig_pool_lock);
-       pool = tcp_md5sig_pool;
-       if (tcp_md5sig_users++ == 0) {
-               alloc = 1;
-               spin_unlock_bh(&tcp_md5sig_pool_lock);
-       } else if (!pool) {
-               tcp_md5sig_users--;
-               spin_unlock_bh(&tcp_md5sig_pool_lock);
-               cpu_relax();
-               goto retry;
-       } else
-               spin_unlock_bh(&tcp_md5sig_pool_lock);
-
-       if (alloc) {
-               /* we cannot hold spinlock here because this may sleep. */
-               struct tcp_md5sig_pool __percpu *p;
-
-               p = __tcp_alloc_md5sig_pool(sk);
-               spin_lock_bh(&tcp_md5sig_pool_lock);
-               if (!p) {
-                       tcp_md5sig_users--;
-                       spin_unlock_bh(&tcp_md5sig_pool_lock);
-                       return NULL;
-               }
-               pool = tcp_md5sig_pool;
-               if (pool) {
-                       /* oops, it has already been assigned. */
-                       spin_unlock_bh(&tcp_md5sig_pool_lock);
-                       __tcp_free_md5sig_pool(p);
-               } else {
-                       tcp_md5sig_pool = pool = p;
-                       spin_unlock_bh(&tcp_md5sig_pool_lock);
-               }
+       if (unlikely(!tcp_md5sig_pool)) {
+               mutex_lock(&tcp_md5sig_mutex);
+
+               if (!tcp_md5sig_pool)
+                       __tcp_alloc_md5sig_pool();
+
+               mutex_unlock(&tcp_md5sig_mutex);
        }
-       return pool;
+       return tcp_md5sig_pool != NULL;
 }
 EXPORT_SYMBOL(tcp_alloc_md5sig_pool);
 
@@ -2977,28 +2934,15 @@ struct tcp_md5sig_pool *tcp_get_md5sig_pool(void)
        struct tcp_md5sig_pool __percpu *p;
 
        local_bh_disable();
-
-       spin_lock(&tcp_md5sig_pool_lock);
-       p = tcp_md5sig_pool;
-       if (p)
-               tcp_md5sig_users++;
-       spin_unlock(&tcp_md5sig_pool_lock);
-
+       p = ACCESS_ONCE(tcp_md5sig_pool);
        if (p)
-               return this_cpu_ptr(p);
+               return __this_cpu_ptr(p);
 
        local_bh_enable();
        return NULL;
 }
 EXPORT_SYMBOL(tcp_get_md5sig_pool);
 
-void tcp_put_md5sig_pool(void)
-{
-       local_bh_enable();
-       tcp_free_md5sig_pool();
-}
-EXPORT_SYMBOL(tcp_put_md5sig_pool);
-
 int tcp_md5_hash_header(struct tcp_md5sig_pool *hp,
                        const struct tcphdr *th)
 {