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[89.253.118.72]) by smtp.gmail.com with ESMTPSA id l10-20020a056512110a00b00498f570aef2sm115503lfg.209.2022.09.19.22.08.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Sep 2022 22:08:50 -0700 (PDT) Message-ID: <66157118-30e6-13af-a0b2-33ec469f1cbc@gmail.com> Date: Tue, 20 Sep 2022 07:08:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.1 Subject: Re: CM-ITC, pch_can/c_can_pci, sendto() returning ENOBUFS Content-Language: en-US To: Vincent Mailhol Cc: Marc Kleine-Budde , dariobin@libero.it, Oliver Hartkopp , linux-can@vger.kernel.org, wg@grandegger.com References: <15a8084b-9617-2da1-6704-d7e39d60643b@gmail.com> <403e18fe-8695-cd56-38f3-0ffe3ec9e472@gmail.com> <36d0419b-297f-8e39-8843-051b55b8a2bb@gmail.com> <986401a8-5f5a-0705-82c4-4df339509e07@gmail.com> <556866e2-a3aa-9077-8db7-edc4ced69491@hartkopp.net> <0eb1dd1b-427a-92c5-22ef-97c557cfec6e@gmail.com> <20220905155416.pgvseb6uggc67ua4@pengutronix.de> <8c481a4e-9493-25ae-f4d7-c12dc98bc83e@gmail.com> <02aeeca7-5958-60f1-3011-fa3aae4ef6b5@gmail.com> From: Jacob Kroon In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-can@vger.kernel.org Hi Vincent, On 9/20/22 03:23, Vincent Mailhol wrote: > On Tue. 20 Sep. 2022 at 08:43, Jacob Kroon wrote: >> Hi Marc and Dario, >> >> On 9/16/22 06:14, Jacob Kroon wrote: >> ...> What I do know is that if I revert commit: >>> >>> "can: c_can: cache frames to operate as a true FIFO" >>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=387da6bc7a826cc6d532b1c0002b7c7513238d5f >>> >>> then everything looks good. I don't get any BUG messages, and the host >>> has been running overnight without problems, so it seems to have fixed >>> the network interface lockup as well. >> >> I ran the kernel *with* the commit above, and also with the following patch: >> >>> diff --git a/drivers/net/can/c_can/c_can_main.c b/drivers/net/can/c_can/c_can_main.c >>> index 52671d1ea17d..4375dc70e21f 100644 >>> --- a/drivers/net/can/c_can/c_can_main.c >>> +++ b/drivers/net/can/c_can/c_can_main.c >>> @@ -1,3 +1,4 @@ >>> +#define DEBUG >>> /* >>> * CAN bus driver for Bosch C_CAN controller >>> * >>> @@ -469,8 +470,15 @@ static netdev_tx_t c_can_start_xmit(struct sk_buff *skb, >>> if (c_can_get_tx_free(tx_ring) == 0) >>> netif_stop_queue(dev); >>> >>> - if (idx < c_can_get_tx_tail(tx_ring)) >>> + netdev_dbg(dev, "JAKR:%d:%d:%d:%d\n", idx, >>> + c_can_get_tx_head(tx_ring), >>> + c_can_get_tx_tail(tx_ring), >>> + c_can_get_tx_free(tx_ring)); >>> + >>> + if (idx < c_can_get_tx_tail(tx_ring)) { >>> cmd &= ~IF_COMM_TXRQST; /* Cache the message */ >>> + netdev_dbg(dev, "JAKR:Caching messages\n"); >>> + } >>> >>> /* Store the message in the interface so we can call >>> * can_put_echo_skb(). We must do this before we enable >> >> and I've uploaded the entire log I could capture from /dev/kmsg, right >> up to the hang, here: >> >> https://pastebin.com/6hvAcPc9 >> >> What looks odd to me right from the start is that sometimes when idx >> rolls over to 0, and *only* when it rolls over to 0, the CAN frame gets >> cached because "idx < c_can_get_tx_tail(tx_ring)". > > This looks like a classic integer wraparound issue. A cast to s32 > should do the trick: > (s32)idx - c_can_get_tx_tail(tx_ring) < 0 > > This is not tested. I let you double check. You can refer to this > function for an example: > https://elixir.bootlin.com/linux/v5.19/source/drivers/net/can/usb/etas_es58x/es58x_core.c#L336 > I tried that change but there is no change in behaviour, and I don't see why it would make a difference since both expressions "idx" and "c_can_get_tx_tail(tx_ring)" are unsigned expressions to begin with. Regards, Jacob