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packet: fix warnings in rollover lock contention

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Avoid two xchg calls whose return values were unused, causing a
warning on some architectures.

The relevant variable is a hint and read without mutual exclusion.
This fix makes all writers hold the receive_queue lock.

Suggested-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Willem de Bruijn 2015-05-14 15:25:02 -04:00 committed by David S. Miller
parent 4ffd3c730e
commit 54d7c01d3e
1 changed files with 5 additions and 10 deletions
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13
net/packet/af_packet.c
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@ -1301,17 +1301,12 @@ static int packet_rcv_has_room(struct packet_sock *po, struct sk_buff *skb)
int ret;
bool has_room;
if (po->prot_hook.func == tpacket_rcv) {
spin_lock(&po->sk.sk_receive_queue.lock);
spin_lock_bh(&po->sk.sk_receive_queue.lock);
ret = __packet_rcv_has_room(po, skb);
spin_unlock(&po->sk.sk_receive_queue.lock);
} else {
ret = __packet_rcv_has_room(po, skb);
}
has_room = ret == ROOM_NORMAL;
if (po->pressure == has_room)
xchg(&po->pressure, !has_room);
po->pressure = !has_room;
spin_unlock_bh(&po->sk.sk_receive_queue.lock);
return ret;
}
@ -3814,7 +3809,7 @@ static unsigned int packet_poll(struct file *file, struct socket *sock,
mask |= POLLIN | POLLRDNORM;
}
if (po->pressure && __packet_rcv_has_room(po, NULL) == ROOM_NORMAL)
xchg(&po->pressure, 0);
po->pressure = 0;
spin_unlock_bh(&sk->sk_receive_queue.lock);
spin_lock_bh(&sk->sk_write_queue.lock);
if (po->tx_ring.pg_vec) {