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authorEric Dumazet <edumazet@google.com>2012-07-29 19:20:37 -0400
committerDavid S. Miller <davem@davemloft.net>2012-07-30 17:53:22 -0400
commit404e0a8b6a55d5e1cd138c6deb1bca9abdf75d8c (patch)
tree38e9748d38c415cc97b973fecb9279cd43f76393 /Documentation
parentcca32e4bf999a34ac08d959f351f2b30bcd02460 (diff)
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 <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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