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udp: udp_rmem_release() should touch sk_rmem_alloc later 

In flood situations, keeping sk_rmem_alloc at a high value
prevents producers from touching the socket.

It makes sense to lower sk_rmem_alloc only at the end
of udp_rmem_release() after the thread draining receive
queue in udp_recvmsg() finished the writes to sk_forward_alloc.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-12-08 11:41:57 -08:00 committed by David S. Miller
parent 6b229cf77d
commit 02ab0d139c
1 changed files with 2 additions and 1 deletions
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3
net/ipv4/udp.c
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@ -1191,13 +1191,14 @@ static void udp_rmem_release(struct sock *sk, int size, int partial)
}
up->forward_deficit = 0;
atomic_sub(size, &sk->sk_rmem_alloc);
sk->sk_forward_alloc += size;
amt = (sk->sk_forward_alloc - partial) & ~(SK_MEM_QUANTUM - 1);
sk->sk_forward_alloc -= amt;
if (amt)
__sk_mem_reduce_allocated(sk, amt >> SK_MEM_QUANTUM_SHIFT);
atomic_sub(size, &sk->sk_rmem_alloc);
}
/* Note: called with sk_receive_queue.lock held.