netdev - [PATCH ipsec-next] xfrm: state lookup can be lockless

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Message-Id: <1474379126-32550-1-git-send-email-fw@strlen.de>
Date:   Tue, 20 Sep 2016 15:45:26 +0200
From:   Florian Westphal <fw@...len.de>
To:     <netdev@...r.kernel.org>
Cc:     Florian Westphal <fw@...len.de>
Subject: [PATCH ipsec-next] xfrm: state lookup can be lockless

This is called from the packet input path, we get lock contention
if many cpus handle ipsec in parallel.

After recent rcu conversion it is safe to call __xfrm_state_lookup
without the spinlock.

Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/xfrm/xfrm_state.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index ba8bf51..a38fdea 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -1431,9 +1431,9 @@ xfrm_state_lookup(struct net *net, u32 mark, const xfrm_address_t *daddr, __be32
 {
 	struct xfrm_state *x;
 
-	spin_lock_bh(&net->xfrm.xfrm_state_lock);
+	rcu_read_lock();
 	x = __xfrm_state_lookup(net, mark, daddr, spi, proto, family);
-	spin_unlock_bh(&net->xfrm.xfrm_state_lock);
+	rcu_read_unlock();
 	return x;
 }
 EXPORT_SYMBOL(xfrm_state_lookup);
-- 
2.7.3