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tcp: avoid a possible divide by zero

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sysctl_tcp_tso_win_divisor might be set to zero while one cpu runs in
tcp_tso_should_defer(). Make sure we dont allow a divide by zero by
reading sysctl_tcp_tso_win_divisor exactly once.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2010-12-07 12:03:55 +00:00 committed by David S. Miller
parent c7757fdb41
commit ad9f4f50fe
1 changed files with 4 additions and 2 deletions
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6
net/ipv4/tcp_output.c
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@ -1512,6 +1512,7 @@ static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
struct tcp_sock *tp = tcp_sk(sk);
const struct inet_connection_sock *icsk = inet_csk(sk);
u32 send_win, cong_win, limit, in_flight;
int win_divisor;
if (TCP_SKB_CB(skb)->flags & TCPHDR_FIN)
goto send_now;
@ -1543,13 +1544,14 @@ static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
goto send_now;
if (sysctl_tcp_tso_win_divisor) {
win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
if (win_divisor) {
u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
/* If at least some fraction of a window is available,
* just use it.
*/
chunk /= sysctl_tcp_tso_win_divisor;
chunk /= win_divisor;
if (limit >= chunk)
goto send_now;
} else {