From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Hartkopp Subject: Re: skbuff panic Date: Sun, 06 Jul 2014 18:13:12 +0200 Message-ID: <53B97598.50400@hartkopp.net> References: <53B7D63B.2060108@hartkopp.net> <53B8504C.4070808@hartkopp.net> <53B93D45.5090505@hartkopp.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mo4-p00-ob.smtp.rzone.de ([81.169.146.160]:34891 "EHLO mo4-p00-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751874AbaGFQNQ (ORCPT ); Sun, 6 Jul 2014 12:13:16 -0400 In-Reply-To: <53B93D45.5090505@hartkopp.net> Sender: linux-can-owner@vger.kernel.org List-ID: To: Austin Schuh Cc: linux-can@vger.kernel.org Answering myself: I tested the latest 3.16.0-rc3-00149-g034a0f6 with tst-packet.c and it works like charm. Receiving and sending with tst-packet is no problem. I was using the SJA1000 based EMS PCMCIA card in my laptop for this test. So I really wonder why (obviously) a CAN frame is processed by the PF_PACKET reception handler at the start of your system?!? Regards, Oliver On 06.07.2014 14:12, Oliver Hartkopp wrote: > On 06.07.2014 07:07, Austin Schuh wrote: > >> What makes you think that someone opened a PF_PACKET socket? I'm >> curious, since that observation may help me produce a more reliable >> test case and debug it some more myself. > > If you look in your call trace is says: > > skb_push+0x38/0x39 (-->> which panics) > packet_rcv_spkt+0x98/0xdf > __netif_receive_skb_core+0x459/0x4dc > get_parent_ip+0xe/0x3e > __netif_receive_skb+0x53/0x65 > > As packet_rcv_spkt() is located in net/packet/af_packet.c there must be some > user at this early stage of system boot to make PF_PACKET process the CAN frame. > > In https://gitorious.org/linux-can/can-tests there's a tst-packet.c program > which uses the PF_PACKET socket to send/receive CAN frames. > > I was using tst-packet.c about four years ago for a test - without any > problems. But maybe something in the network layer changed, so that CAN frame > skbs need to be created with a different setup now. > > I'll try ASAP if tst-packet.c still works as expected on my machine. > >> >> I'm going to work on reproducing the panic more reliable, and then >> I'll give your patch a whirl. Currently, only PCs that are on the >> other end of cell modems out in the field seem to be triggering the >> panic. I'm hesitant to do excessive experimentation on something that >> takes a plane trip to fix. That just means that this will take longer >> to debug that I'd like... > > Indeed this should not be the plan ... > Let's save the world by saving carbon dioxide ;-) > > Best regards, > Oliver > > -- > To unsubscribe from this list: send the line "unsubscribe linux-can" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >