From owner-freebsd-net@FreeBSD.ORG Mon May 7 17:46:13 2012 Return-Path: Delivered-To: net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id D51651065677; Mon, 7 May 2012 17:46:13 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from bigwig.baldwin.cx (bigknife-pt.tunnel.tserv9.chi1.ipv6.he.net [IPv6:2001:470:1f10:75::2]) by mx1.freebsd.org (Postfix) with ESMTP id 7A3F68FC17; Mon, 7 May 2012 17:46:13 +0000 (UTC) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id B4A2AB995; Mon, 7 May 2012 13:46:12 -0400 (EDT) From: John Baldwin To: Konstantin Belousov Date: Mon, 7 May 2012 13:44:57 -0400 User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110714-p13; KDE/4.5.5; amd64; ; ) References: <20120407133715.GU2358@deviant.kiev.zoral.com.ua> <201205041130.22202.jhb@freebsd.org> <20120504221819.GS2358@deviant.kiev.zoral.com.ua> In-Reply-To: <20120504221819.GS2358@deviant.kiev.zoral.com.ua> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <201205071344.58041.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Mon, 07 May 2012 13:46:12 -0400 (EDT) Cc: jfv@freebsd.org, Jack Vogel , net@freebsd.org Subject: Re: 82574L hangs (with r233708 e1000 driver). X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 07 May 2012 17:46:13 -0000 On Friday, May 04, 2012 6:18:19 pm Konstantin Belousov wrote: > On Fri, May 04, 2012 at 11:30:22AM -0400, John Baldwin wrote: > > On Tuesday, May 01, 2012 12:21:21 pm Konstantin Belousov wrote: > > > On Thu, Apr 12, 2012 at 09:38:49PM +0300, Konstantin Belousov wrote: > > > > On Mon, Apr 09, 2012 at 12:19:39PM -0400, John Baldwin wrote: > > > > > On Sunday, April 08, 2012 1:11:25 am Konstantin Belousov wrote: > > > > > > On Sat, Apr 07, 2012 at 04:22:07PM -0700, Jack Vogel wrote: > > > > > > > Make sure you have any firmware up to the latest available, if that > > doesn't > > > > > > > help > > > > > > > let me know and I'll check internally to see if there are any > > outstanding > > > > > > > issues > > > > > > > in shared code, that will be after the weekend. > > > > > > > > > > > > I had BIOS rev. 151, after you hint I found rev. 154 on the site. > > > > > > Now BIOS reports itself as MTCDT10N.86A.0154.2012.0323.1601, > > > > > > March 23. > > > > > > > > > > > > Unfortunately, upgrade did not changed anything in regard of hanging > > > > > > interface. > > > > > > > > > > Does reverting 233708 make any difference? Have you tried futzing > > around with > > > > > kgdb when it is hung to see what state the device is in (software state > > at > > > > > least)? > > > > It does, in a sense that without r233708 the interface becomes stuck > > > > almost immediately. I just upgraded to the e1000@r234154, which does not > > > > change much. > > > > > > > > I fiddled with the adapter state after the hang in kgdb more, and I > > > > noted something interesting. Apparently, tx works. When I ping the remote > > > > host from my suffering atom machine, remote host sees the packet. Also > > > > remote machine sees some udp traffic originating from the tom, like > > > > ntp queries. > > > > > > > > And, on receive, the atom board does receive interrupts, em0:rx 0 counter > > > > in vmstat -i increases. Even more fun, the sysctl dev.em.0.debug > > > > shows increasing hw rdh (as I understand, this is hardware 'last > > > > received' packet pointer for rx ring). So I looked at the packet > > > > descriptor at hw rdt index, and there I see > > > > (kgdb) p/x ((struct adapter *)0xffffff80010e4000)->rx_rings->rx_base[78] > > > > $11 = {buffer_addr = 0x12a128800, length = 0x5ea, csum = 0x3c2b, status = > > 0x0, > > > > errors = 0x0, special = 0x0} > > > > > > > > Apparently, the Descriptor Done bit is clear, so the em_rxeof() function > > > > breaks from the loop, not consuming the current packet. Also, it returns > > > > false due to DD bit clear. This prevents em_msix_rx() from scheduling > > > > taskqueue for processing. So apparent cause for the hang is missing > > > > DD bit in descriptor. > > > > > > > > I am not sure isn't all this is obvious for anybody who knows em > > > > internals, and were to go from there. > > > > > > Ok, nobody cares. > > > > > > Below is the workaround I use to prevent the interface wedging. > > > It seems that the sole PCI register read (namely, the rx ring head read) > > > and consequent recheck of the descriptor status greatly reduce the > > > likelihood of the issue. Unfortunately, the read does not eliminate > > > the hang completely. So it is not some PCIe coherency problem. > > > > > > With the patch applied, I am able to copy around blu-ray images, while > > > previously the interface hang in 20-30 seconds of 100Mbit/s traffic. > > > Sometimes the messages are printed: > > > em0: Workaround: head 1018 tail 1002 cur 1010 > > > em0: Workaround: head 976 tail 973 cur 974 > > > em0: Workaround: head 950 tail 939 cur 946 > > > em0: Workaround: head 435 tail 419 cur 426 > > > > > > Machine is still dead due to random memory corruption which I see, in > > > particular, pmap sometimes read garbage from PTEs. I have no idea is > > > it related to em0 rx descriptor missed writes, or is a different issue. > > > > Humm, so if I'm reading this correctly, the card "skips" a receive > > descriptor and stores a packet at the next descriptor? That's just > > bizarre. > Either this, or it does store the packet but 'forgots' to update the > rx descriptor. I think that your interpretation is closer to reality, > since I get sustained 20MB/s over ssh with the patch even when workaround > activates. The lost packets probably should cause retransmit and speed > drop. This is just weird. I wonder if there is a known errata for this? This really seems to be broken hardware and not a driver issue. -- John Baldwin