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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2010-06-16 08:47:39 +0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2010-06-16 08:47:39 +0400 |
| commit | 5f2f89209500623ccb4713ec4af7de86fd30a9e4 (patch) | |
| tree | 6a48b8183ac6d60d8ce6a9c907de1ea35c1ca918 /net | |
| parent | d5f31fbfd8fa3836a918592032853c41d1797c3d (diff) | |
| download | linux-5f2f89209500623ccb4713ec4af7de86fd30a9e4.tar.xz | |
inetpeer: do not use zero refcnt for freed entries
Followup of commit aa1039e73cc2 (inetpeer: RCU conversion)
Unused inet_peer entries have a null refcnt.
Using atomic_inc_not_zero() in rcu lookups is not going to work for
them, and slow path is taken.
Fix this using -1 marker instead of 0 for deleted entries.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/inetpeer.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c index 58fbc7e2475e..349249fad2db 100644 --- a/net/ipv4/inetpeer.c +++ b/net/ipv4/inetpeer.c @@ -187,7 +187,12 @@ static struct inet_peer *lookup_rcu_bh(__be32 daddr) while (u != peer_avl_empty) { if (daddr == u->v4daddr) { - if (unlikely(!atomic_inc_not_zero(&u->refcnt))) + /* Before taking a reference, check if this entry was + * deleted, unlink_from_pool() sets refcnt=-1 to make + * distinction between an unused entry (refcnt=0) and + * a freed one. + */ + if (unlikely(!atomic_add_unless(&u->refcnt, 1, -1))) u = NULL; return u; } @@ -322,8 +327,9 @@ static void unlink_from_pool(struct inet_peer *p) * in cleanup() function to prevent sudden disappearing. If we can * atomically (because of lockless readers) take this last reference, * it's safe to remove the node and free it later. + * We use refcnt=-1 to alert lockless readers this entry is deleted. */ - if (atomic_cmpxchg(&p->refcnt, 1, 0) == 1) { + if (atomic_cmpxchg(&p->refcnt, 1, -1) == 1) { struct inet_peer **stack[PEER_MAXDEPTH]; struct inet_peer ***stackptr, ***delp; if (lookup(p->v4daddr, stack) != p) |