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udp: ipv4: do not use sk_dst_lock from softirq context

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Using sk_dst_lock from softirq context is not supported right now.

Instead of adding BH protection everywhere,
udp_sk_rx_dst_set() can instead use xchg(), as suggested
by David.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Fixes: 9750223102 ("udp: ipv4: must add synchronization in udp_sk_rx_dst_set()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2013-12-15 10:53:46 -08:00 • committed by David S. Miller
commit e47eb5dfb2
1 changed files with 4 additions and 9 deletions
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9
net/ipv4/udp.c
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@ -1600,20 +1600,15 @@ static void flush_stack(struct sock **stack, unsigned int count,
} }
/* For TCP sockets, sk_rx_dst is protected by socket lock /* For TCP sockets, sk_rx_dst is protected by socket lock
* For UDP, we use sk_dst_lock to guard against concurrent changes. * For UDP, we use xchg() to guard against concurrent changes.
*/ */
static void udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst) static void udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst)
{ {
struct dst_entry *old; struct dst_entry *old;
spin_lock(&sk->sk_dst_lock);
old = sk->sk_rx_dst;
if (likely(old != dst)) {
dst_hold(dst); dst_hold(dst);
sk->sk_rx_dst = dst; old = xchg(&sk->sk_rx_dst, dst);
dst_release(old); dst_release(old);
}
spin_unlock(&sk->sk_dst_lock);
} }
/* /*