Commit 7b46ac4e authored by David S. Miller's avatar David S. Miller
Browse files

inetpeer: Don't disable BH for initial fast RCU lookup. 



If modifications on other cpus are ok, then modifications to
the tree during lookup done by the local cpu are ok too.

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5217e879

net/ipv4/inetpeer.c

+9 −9
Original line number Diff line number Diff line
@@ -206,16 +206,16 @@ static int addr_compare(const struct inetpeer_addr *a, 
})



/*

 * Called with rcu_read_lock_bh()

 * Called with rcu_read_lock()

 * Because we hold no lock against a writer, its quite possible we fall

 * in an endless loop.

 * But every pointer we follow is guaranteed to be valid thanks to RCU.

 * We exit from this function if number of links exceeds PEER_MAXDEPTH

 */

static struct inet_peer *lookup_rcu_bh(const struct inetpeer_addr *daddr,

static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,

				    struct inet_peer_base *base)

{

	struct inet_peer *u = rcu_dereference_bh(base->root);

	struct inet_peer *u = rcu_dereference(base->root);

	int count = 0;



	while (u != peer_avl_empty) {
@@ -231,9 +231,9 @@ static struct inet_peer *lookup_rcu_bh(const struct inetpeer_addr *daddr, 
			return u;

		}

		if (cmp == -1)

			u = rcu_dereference_bh(u->avl_left);

			u = rcu_dereference(u->avl_left);

		else

			u = rcu_dereference_bh(u->avl_right);

			u = rcu_dereference(u->avl_right);

		if (unlikely(++count == PEER_MAXDEPTH))

			break;

	}
@@ -470,11 +470,11 @@ struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create) 
	/* Look up for the address quickly, lockless.

	 * Because of a concurrent writer, we might not find an existing entry.

	 */

	rcu_read_lock_bh();

	rcu_read_lock();

	sequence = read_seqbegin(&base->lock);

	p = lookup_rcu_bh(daddr, base);

	p = lookup_rcu(daddr, base);

	invalidated = read_seqretry(&base->lock, sequence);

	rcu_read_unlock_bh();

	rcu_read_unlock();



	if (p) {

		/* The existing node has been found.