diff options
| -rw-r--r-- | net/ipv4/inetpeer.c | 42 |
1 files changed, 27 insertions, 15 deletions
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c index 9df4e63..ce616d9 100644 --- a/net/ipv4/inetpeer.c +++ b/net/ipv4/inetpeer.c @@ -154,11 +154,9 @@ void __init inet_initpeers(void) /* Called with or without local BH being disabled. */ static void unlink_from_unused(struct inet_peer *p) { - if (!list_empty(&p->unused)) { - spin_lock_bh(&unused_peers.lock); - list_del_init(&p->unused); - spin_unlock_bh(&unused_peers.lock); - } + spin_lock_bh(&unused_peers.lock); + list_del_init(&p->unused); + spin_unlock_bh(&unused_peers.lock); } static int addr_compare(const struct inetpeer_addr *a, @@ -205,6 +203,20 @@ static int addr_compare(const struct inetpeer_addr *a, u; \ }) +static bool atomic_add_unless_return(atomic_t *ptr, int a, int u, int *newv) +{ + int cur, old = atomic_read(ptr); + + while (old != u) { + *newv = old + a; + cur = atomic_cmpxchg(ptr, old, *newv); + if (cur == old) + return true; + old = cur; + } + return false; +} + /* * Called with rcu_read_lock() * Because we hold no lock against a writer, its quite possible we fall @@ -213,7 +225,8 @@ static int addr_compare(const struct inetpeer_addr *a, * We exit from this function if number of links exceeds PEER_MAXDEPTH */ static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr, - struct inet_peer_base *base) + struct inet_peer_base *base, + int *newrefcnt) { struct inet_peer *u = rcu_dereference(base->root); int count = 0; @@ -226,7 +239,7 @@ static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr, * distinction between an unused entry (refcnt=0) and * a freed one. */ - if (unlikely(!atomic_add_unless(&u->refcnt, 1, -1))) + if (!atomic_add_unless_return(&u->refcnt, 1, -1, newrefcnt)) u = NULL; return u; } @@ -465,22 +478,23 @@ struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create) struct inet_peer_base *base = family_to_base(daddr->family); struct inet_peer *p; unsigned int sequence; - int invalidated; + int invalidated, newrefcnt = 0; /* Look up for the address quickly, lockless. * Because of a concurrent writer, we might not find an existing entry. */ rcu_read_lock(); sequence = read_seqbegin(&base->lock); - p = lookup_rcu(daddr, base); + p = lookup_rcu(daddr, base, &newrefcnt); invalidated = read_seqretry(&base->lock, sequence); rcu_read_unlock(); if (p) { - /* The existing node has been found. +found: /* The existing node has been found. * Remove the entry from unused list if it was there. */ - unlink_from_unused(p); + if (newrefcnt == 1) + unlink_from_unused(p); return p; } @@ -494,11 +508,9 @@ struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create) write_seqlock_bh(&base->lock); p = lookup(daddr, stack, base); if (p != peer_avl_empty) { - atomic_inc(&p->refcnt); + newrefcnt = atomic_inc_return(&p->refcnt); write_sequnlock_bh(&base->lock); - /* Remove the entry from unused list if it was there. */ - unlink_from_unused(p); - return p; + goto found; } p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL; if (p) { |
