On Tue, 2012-08-21 at 23:07 -0500, Larry Finger wrote: > Hi, > > The commit entitled "tcp: reduce out_of_order memory use" turns out to cause > problems with a number of USB drivers. > > The first one called to my attention was for staging/r8712u. For this driver, > there are problems with SSL communications as reported in > https://bugzilla.redhat.com/show_bug.cgi?id=847525. > > Other drivers including rtl8187, rtl8192cu and rt2800usb cannot connect to a > WPA1- or WEP-encrypted AP, but work fine with WPA2. The rtl8192cu problem is > reported in https://bugzilla.kernel.org/show_bug.cgi?id=46171. > > I find it hard to understand why this patch should cause these effects; however, > I have verified that a kernel generated from "git checkout e86b2919" works fine. > This commit is immediately before the patch in question. > > Note, this patch was applied during the merge between 3.3 and 3.4. The > regression has been undiscovered for some time. > > Any help on this problem will be appreciated. > > Larry This particular commit is the start of a patches batch that ended in the generic TCP coalescing mechanism. It is known to have problem on drivers doing skb_clone() in their rx path. Current kernels should be ok, because coalescing doesnt happen if the destination skb is cloned (skb_cloned(to) in skb_try_coalesce()) For 3.4 kernel, I guess I need to backport this skb_cloned(to) check fo stable 3.4 kernel But these skb_clone() in various USB drivers should be killed for good, they really can kill the box because of skb->truesize lies. Please test following patch (for 3.4 kernels) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 257b617..c45ac2d 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4496,7 +4496,9 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb) * to avoid future tcp_collapse_ofo_queue(), * probably the most expensive function in tcp stack. */ - if (skb->len <= skb_tailroom(skb1) && !tcp_hdr(skb)->fin) { + if (skb->len <= skb_tailroom(skb1) && + !skb_cloned(skb1) && + !tcp_hdr(skb)->fin) { NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE); BUG_ON(skb_copy_bits(skb, 0, -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
