From: Eric Dumazet <edumazet@google.com>
Date: Mon, 20 May 2013 06:52:26 +0000 (+0000)
Subject: tcp: md5: remove spinlock usage in fast path
X-Git-Tag: v3.2.66~6
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=10f2216850e5955d102f8a052f5f3621e1aca328;p=pandora-kernel.git

tcp: md5: remove spinlock usage in fast path

commit 71cea17ed39fdf1c0634f530ddc6a2c2fc601c2b upstream.

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 <edumazet@google.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2:
 - Adjust context
 - Conditions for alloc/free are quite different]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 238255b27106..e90235fb1b18 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1214,11 +1214,13 @@ extern int tcp_v4_md5_do_del(struct sock *sk, __be32 addr);
 #define tcp_twsk_md5_key(twsk)	NULL
 #endif
 
-extern struct tcp_md5sig_pool __percpu *tcp_alloc_md5sig_pool(struct sock *);
-extern void tcp_free_md5sig_pool(void);
+extern bool tcp_alloc_md5sig_pool(void);
 
 extern struct tcp_md5sig_pool	*tcp_get_md5sig_pool(void);
-extern void tcp_put_md5sig_pool(void);
+static inline void tcp_put_md5sig_pool(void)
+{
+	local_bh_enable();
+}
 
 extern int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
 extern int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
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