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authorEric Dumazet <eric.dumazet@gmail.com>2012-07-31 01:08:23 +0000
committerDavid S. Miller <davem@davemloft.net>2012-07-31 14:41:38 -0700
commit54764bb647b2e847c512acf8d443df965da35000 (patch)
tree3918f6f42679d0ebdcef230f28285f99d178be62 /net/core
parent5a0d513b622ee41e117fc37e26e27e8ef42e8dae (diff)
downloadop-kernel-dev-54764bb647b2e847c512acf8d443df965da35000.zip
op-kernel-dev-54764bb647b2e847c512acf8d443df965da35000.tar.gz
ipv4: Restore old dst_free() behavior.
commit 404e0a8b6a55 (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>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/dst.c26
1 files changed, 5 insertions, 21 deletions
diff --git a/net/core/dst.c b/net/core/dst.c
index d9e33ebe..069d51d 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -258,15 +258,6 @@ again:
}
EXPORT_SYMBOL(dst_destroy);
-static void dst_rcu_destroy(struct rcu_head *head)
-{
- struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
-
- dst = dst_destroy(dst);
- if (dst)
- __dst_free(dst);
-}
-
void dst_release(struct dst_entry *dst)
{
if (dst) {
@@ -274,14 +265,10 @@ void dst_release(struct dst_entry *dst)
newrefcnt = atomic_dec_return(&dst->__refcnt);
WARN_ON(newrefcnt < 0);
- if (unlikely(dst->flags & (DST_NOCACHE | DST_RCU_FREE)) && !newrefcnt) {
- if (dst->flags & DST_RCU_FREE) {
- call_rcu_bh(&dst->rcu_head, dst_rcu_destroy);
- } else {
- dst = dst_destroy(dst);
- if (dst)
- __dst_free(dst);
- }
+ if (unlikely(dst->flags & DST_NOCACHE) && !newrefcnt) {
+ dst = dst_destroy(dst);
+ if (dst)
+ __dst_free(dst);
}
}
}
@@ -333,14 +320,11 @@ EXPORT_SYMBOL(__dst_destroy_metrics_generic);
*/
void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst)
{
- bool hold;
-
WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
/* If dst not in cache, we must take a reference, because
* dst_release() will destroy dst as soon as its refcount becomes zero
*/
- hold = (dst->flags & (DST_NOCACHE | DST_RCU_FREE)) == DST_NOCACHE;
- if (unlikely(hold)) {
+ if (unlikely(dst->flags & DST_NOCACHE)) {
dst_hold(dst);
skb_dst_set(skb, dst);
} else {
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