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 --- net/decnet/dn_route.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'net/decnet') diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c index 85a3604c87c8..26719779ad8e 100644 --- a/net/decnet/dn_route.c +++ b/net/decnet/dn_route.c @@ -184,6 +184,12 @@ static __inline__ unsigned int dn_hash(__le16 src, __le16 dst) return dn_rt_hash_mask & (unsigned int)tmp; } +static inline void dst_rcu_free(struct rcu_head *head) +{ + struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head); + dst_free(dst); +} + static inline void dnrt_free(struct dn_route *rt) { call_rcu_bh(&rt->dst.rcu_head, dst_rcu_free); -- cgit v1.2.3