From: Eric Dumazet Date: Sun, 29 Jul 2012 23:20:37 +0000 (+0000) Subject: net: ipv4: fix RCU races on dst refcounts X-Git-Tag: v3.6-rc1~30^2~6 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=404e0a8b6a55d5e1cd138c6deb1bca9abdf75d8c;p=pandora-kernel.git 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 --- Reading git-diff-tree failed