From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dean Jenkins Subject: Re: [PATCH] asix: Fix offset calculation in asix_rx_fixup() causing slow transmissions Date: Wed, 18 May 2016 00:01:03 +0100 Message-ID: <573BA2AF.3090006@mentor.com> References: <1463456175-6674-1-git-send-email-john.stultz@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Cc: "David B. Robins" , Mark Craske , Emil Goode , "David S. Miller" , YongQin Liu , Guodong Xu , Ivan Vecera , , , stable To: John Stultz , lkml Return-path: In-Reply-To: <1463456175-6674-1-git-send-email-john.stultz@linaro.org> Sender: stable-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hi John, Thanks for your patch. I think the patch has already been applied. The git commit subject of "asix: Fix offset calculation in asix_rx_fixup() causing slow transmissions" I think is a bit misleading as the bug relates to reception and not transmission. I guess that your intent was to say that "the through-put of communications was low" due to the bug. Personally, I would of used a git subject like "asix: Fix asix_rx_fixup_interval() offset calculation for spanned frames" But anyway, I have no real issue with the patch. On 17/05/16 04:36, John Stultz wrote: > In testing with HiKey, we found that since > commit 3f30b158eba5 ("asix: On RX avoid creating bad Ethernet > frames"), > we're seeing lots of noise during network transfers: > > [ 239.027993] asix 1-1.1:1.0 eth0: asix_rx_fixup() Data Header synchronisation was lost, remaining 988 > [ 239.037310] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0x54ebb5ec, offset 4 > [ 239.045519] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0xcdffe7a2, offset 4 > [ 239.275044] asix 1-1.1:1.0 eth0: asix_rx_fixup() Data Header synchronisation was lost, remaining 988 > [ 239.284355] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0x1d36f59d, offset 4 > [ 239.292541] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0xaef3c1e9, offset 4 > [ 239.518996] asix 1-1.1:1.0 eth0: asix_rx_fixup() Data Header synchronisation was lost, remaining 988 > [ 239.528300] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0x2881912, offset 4 > [ 239.536413] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0x5638f7e2, offset 4 > > And network throughput ends up being pretty bursty and slow with > a overall throughput of at best ~30kB/s (where as previously we > got 1.1MB/s with the slower USB1.1 "full speed" host). > > We found the issue also was reproducible on a x86_64 system, > using a "high-speed" USB2.0 port but the throughput did not > measurably drop (possibly due to the scp transfer being cpu > bound on my slow test hardware). > > After lots of debugging, I found the check added in the > problematic commit seems to be calculating the offset > incorrectly. > > In the normal case, in the main loop of the function, we do: > (where offset is zero, or set to "offset += (copy_length + 1) & > 0xfffe" in the previous loop) > rx->header = get_unaligned_le32(skb->data + > offset); > offset += sizeof(u32); > > But the problematic patch calculates: > offset = ((rx->remaining + 1) & 0xfffe) + sizeof(u32); > rx->header = get_unaligned_le32(skb->data + offset); > > Adding some debug logic to check those offset calculation used > to find rx->header, the one in problematic code is always too > large by sizeof(u32). > > Thus, this patch removes the incorrect " + sizeof(u32)" addition > in the problematic calculation, and resolves the issue. > > Cc: Dean Jenkins > Cc: "David B. Robins" > Cc: Mark Craske > Cc: Emil Goode > Cc: "David S. Miller" > Cc: YongQin Liu > Cc: Guodong Xu > Cc: Ivan Vecera > Cc: linux-usb@vger.kernel.org > Cc: netdev@vger.kernel.org > Cc: stable #4.4+ > Reported-by: Yongqin Liu > Signed-off-by: John Stultz > --- > drivers/net/usb/asix_common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c > index 0c5c22b..7de5ab5 100644 > --- a/drivers/net/usb/asix_common.c > +++ b/drivers/net/usb/asix_common.c > @@ -66,7 +66,7 @@ int asix_rx_fixup_internal(struct usbnet *dev, struct sk_buff *skb, > * buffer. > */ > if (rx->remaining && (rx->remaining + sizeof(u32) <= skb->len)) { > - offset = ((rx->remaining + 1) & 0xfffe) + sizeof(u32); > + offset = ((rx->remaining + 1) & 0xfffe); I have verified that this fixes my ARM board. Thanks for finding the mistake. Note that the outer set of brackets could of been removed as they are redundant. > rx->header = get_unaligned_le32(skb->data + offset); > offset = 0; > Thanks, Best regards, Dean -- Dean Jenkins Embedded Software Engineer Linux Transportation Solutions Mentor Embedded Software Division Mentor Graphics (UK) Ltd.