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/ipv4/fib_semantics.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net/ipv4/fib_semantics.c') diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index da0cc2e6b250..e55171f184f9 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -172,9 +172,9 @@ static void free_fib_info_rcu(struct rcu_head *head) if (nexthop_nh->nh_exceptions) free_nh_exceptions(nexthop_nh); if (nexthop_nh->nh_rth_output) - dst_free(&nexthop_nh->nh_rth_output->dst); + dst_release(&nexthop_nh->nh_rth_output->dst); if (nexthop_nh->nh_rth_input) - dst_free(&nexthop_nh->nh_rth_input->dst); + dst_release(&nexthop_nh->nh_rth_input->dst); } endfor_nexthops(fi); release_net(fi->fib_net); -- cgit v1.2.3