From 71cea17ed39fdf1c0634f530ddc6a2c2fc601c2b Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 20 May 2013 06:52:26 +0000 Subject: tcp: md5: remove spinlock usage in fast path TCP md5 code uses per cpu variables but protects access to them with a shared spinlock, which is a contention point. [ tcp_md5sig_pool_lock is locked twice per incoming packet ] Makes things much simpler, by allocating crypto structures once, first time a socket needs md5 keys, and not deallocating them as they are really small. Next step would be to allow crypto allocations being done in a NUMA aware way. Signed-off-by: Eric Dumazet Cc: Herbert Xu Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 98 +++++++++++++--------------------------------------------- 1 file changed, 21 insertions(+), 77 deletions(-) (limited to 'net/ipv4/tcp.c') diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index dcb116dde216..53d9c120fbb8 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3095,9 +3095,8 @@ 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) { @@ -3112,30 +3111,14 @@ 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; @@ -3146,53 +3129,27 @@ __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; - bool alloc = false; - -retry: - spin_lock_bh(&tcp_md5sig_pool_lock); - pool = tcp_md5sig_pool; - if (tcp_md5sig_users++ == 0) { - alloc = true; - 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); @@ -3209,28 +3166,15 @@ 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) { -- cgit v1.2.3