From 404e0a8b6a55d5e1cd138c6deb1bca9abdf75d8c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 29 Jul 2012 23:20:37 +0000 Subject: net: ipv4: fix RCU races on dst refcounts commit c6cffba4ffa2 (ipv4: Fix input route performance regression.) added various fatal races with dst refcounts. crashes happen on tcp workloads if routes are added/deleted at the same time. The dst_free() calls from free_fib_info_rcu() are clearly racy. We need instead regular dst refcounting (dst_release()) and make sure dst_release() is aware of RCU grace periods : Add DST_RCU_FREE flag so that dst_release() respects an RCU grace period before dst destruction for cached dst Introduce a new inet_sk_rx_dst_set() helper, using atomic_inc_not_zero() to make sure we dont increase a zero refcount (On a dst currently waiting an rcu grace period before destruction) rt_cache_route() must take a reference on the new cached route, and release it if was not able to install it. With this patch, my machines survive various benchmarks. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/inet_sock.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'include/net/inet_sock.h') diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h index 613cfa401672..e3fd34c83ac9 100644 --- a/include/net/inet_sock.h +++ b/include/net/inet_sock.h @@ -249,4 +249,17 @@ static inline __u8 inet_sk_flowi_flags(const struct sock *sk) return flags; } +static inline void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb) +{ + struct dst_entry *dst = skb_dst(skb); + + if (atomic_inc_not_zero(&dst->__refcnt)) { + if (!(dst->flags & DST_RCU_FREE)) + dst->flags |= DST_RCU_FREE; + + sk->sk_rx_dst = dst; + inet_sk(sk)->rx_dst_ifindex = skb->skb_iif; + } +} + #endif /* _INET_SOCK_H */ -- cgit v1.2.3