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authorEric Dumazet <eric.dumazet@gmail.com>2010-12-07 12:03:55 +0000
committerDavid S. Miller <davem@davemloft.net>2010-12-08 12:34:08 -0800
commitad9f4f50fe9288bbe65b7dfd76d8820afac6a24c (patch)
treef3f3100da8d042607bbbab31c1f8a060ba2b5f15 /net/ipv4/tcp_output.c
parentc7757fdb41dfcf6add9f8a4576eb85aa5e77a4eb (diff)
downloadlwn-ad9f4f50fe9288bbe65b7dfd76d8820afac6a24c.tar.gz
lwn-ad9f4f50fe9288bbe65b7dfd76d8820afac6a24c.zip
tcp: avoid a possible divide by zero
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>
Diffstat (limited to 'net/ipv4/tcp_output.c')
-rw-r--r--net/ipv4/tcp_output.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 3c59ab42df2b..0d4a3cebfb46 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -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 {