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ipv4: Restore old dst_free() behavior.

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commit 404e0a8b6a (net: ipv4: fix RCU races on dst refcounts) tried
to solve a race but added a problem at device/fib dismantle time :

We really want to call dst_free() as soon as possible, even if sockets
still have dst in their cache.
dst_release() calls in free_fib_info_rcu() are not welcomed.

Root of the problem was that now we also cache output routes (in
nh_rth_output), we must use call_rcu() instead of call_rcu_bh() in
rt_free(), because output route lookups are done in process context.

Based on feedback and initial patch from David Miller (adding another
call_rcu_bh() call in fib, but it appears it was not the right fix)

I left the inet_sk_rx_dst_set() helper and added __rcu attributes
to nh_rth_output and nh_rth_input to better document what is going on in
this code.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2012-07-31 01:08:23 +00:00
committed by David S. Miller
parent 5a0d513b62
commit 54764bb647
7 changed files with 50 additions and 50 deletions
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4
include/net/ip_fib.h
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@@ -81,8 +81,8 @@ struct fib_nh {
__be32 nh_gw;
__be32 nh_saddr;
int nh_saddr_genid;
struct rtable *nh_rth_output;
struct rtable *nh_rth_input;
struct rtable __rcu *nh_rth_output;
struct rtable __rcu *nh_rth_input;
struct fnhe_hash_bucket *nh_exceptions;
};