From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 150FE107A3 for ; Wed, 4 Oct 2023 09:55:08 +0000 (UTC) Received: from relay1-d.mail.gandi.net (relay1-d.mail.gandi.net [217.70.183.193]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7138283; Wed, 4 Oct 2023 02:55:05 -0700 (PDT) Received: by mail.gandi.net (Postfix) with ESMTPSA id D888F240018; Wed, 4 Oct 2023 09:55:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1696413304; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=72iAb2IAE4FbKnYSwHehmr/svO5trIG6B6hsbHz2LRA=; b=pbITdmedeBgPSsbb3Nv4CdnsuGLyjUyYddo18Pae2H2Q9hxuubSi1PAWvfw7XiW0t+785/ J/9LPS8C7aUJ9UkTyTmuneHNphvfrDwVv7S/v9WqA0SCSnpNjbEcapq9r+IrNeV8NZF+3p xfBSmpPABBD2C1RTPCub3YtlmHZBLJdvttbgM3tSznYJDsUTdLdKbqKwj81NV630W7ex+q 4XazAHb08EEfTpBkOkaV8TI9qbX6WjXsQEUy2QDhLxRFpW8Ddzd9+siG26Orp2Xq5CVNIC 7kL8sdhGf7J+EeZ9cddC/fXPgyXUvUtoA9qdCKixMg8LRMBb1nk84kjL4YuXAg== Date: Wed, 4 Oct 2023 11:55:00 +0200 From: Miquel Raynal To: Marc Kleine-Budde Cc: Wolfgang Grandegger , "David S. Miller" , Jakub Kicinski , Paolo Abeni , Eric Dumazet , netdev@vger.kernel.org, linux-can@vger.kernel.org, =?UTF-8?B?SsOpcsOpbWll?= Dautheribes , Thomas Petazzoni , sylvain.girard@se.com, pascal.eberhard@se.com, stable@vger.kernel.org Subject: Re: [PATCH v3] can: sja1000: Always restart the Tx queue after an overrun Message-ID: <20231004115500.6648d3c7@xps-13> In-Reply-To: <20231004-uneasy-backed-e01d77be9f51-mkl@pengutronix.de> References: <20231002160206.190953-1-miquel.raynal@bootlin.com> <20231004-uneasy-backed-e01d77be9f51-mkl@pengutronix.de> Organization: Bootlin X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-GND-Sasl: miquel.raynal@bootlin.com X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_BLOCKED, RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_PASS,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Hi Marc, mkl@pengutronix.de wrote on Wed, 4 Oct 2023 11:41:08 +0200: > On 02.10.2023 18:02:06, Miquel Raynal wrote: > > Upstream commit 717c6ec241b5 ("can: sja1000: Prevent overrun stalls with > > a soft reset on Renesas SoCs") fixes an issue with Renesas own SJA1000 > > CAN controller reception: the Rx buffer is only 5 messages long, so when > > the bus loaded (eg. a message every 50us), overrun may easily > > happen. Upon an overrun situation, due to a possible internal crosstalk > > situation, the controller enters a frozen state which only can be > > unlocked with a soft reset (experimentally). The solution was to offload > > a call to sja1000_start() in a threaded handler. This needs to happen in > > process context as this operation requires to sleep. sja1000_start() > > basically enters "reset mode", performs a proper software reset and > > returns back into "normal mode". > >=20 > > Since this fix was introduced, we no longer observe any stalls in > > reception. However it was sporadically observed that the transmit path > > would now freeze. Further investigation blamed the fix mentioned above, > > and especially the reset operation. Reproducing the reset in a loop > > helped identifying what could possibly go wrong. The sja1000 is a single > > Tx queue device, which leverages the netdev helpers to process one Tx > > message at a time. The logic is: the queue is stopped, the message sent > > to the transceiver, once properly transmitted the controller sets a > > status bit which triggers an interrupt, in the interrupt handler the > > transmission status is checked and the queue woken up. Unfortunately, if > > an overrun happens, we might perform the soft reset precisely between > > the transmission of the buffer to the transceiver and the advent of the > > transmission status bit. We would then stop the transmission operation > > without re-enabling the queue, leading to all further transmissions to > > be ignored. > >=20 > > The reset interrupt can only happen while the device is "open", and > > after a reset we anyway want to resume normal operations, no matter if a > > packet to transmit got dropped in the process, so we shall wake up the > > queue. Restarting the device and waking-up the queue is exactly what > > sja1000_set_mode(CAN_MODE_START) does. In order to be consistent about > > the queue state, we must acquire a lock both in the reset handler and in > > the transmit path to ensure serialization of both operations. It turns > > out, a lock is already held when entering the transmit path, so we can > > just acquire/release it as well with the regular net helpers inside the > > threaded interrupt handler and this way we should be safe. As the > > reset handler might still be called after the transmission of a frame to > > the transceiver but before it actually gets transmitted, we must ensure > > we don't leak the skb, so we free it (the behavior is consistent, no > > matter if there was an skb on the stack or not). > >=20 > > Fixes: 717c6ec241b5 ("can: sja1000: Prevent overrun stalls with a soft = reset on Renesas SoCs") > > Cc: stable@vger.kernel.org > > Signed-off-by: Miquel Raynal =20 >=20 > Have you compile tested this against current net/main? >=20 > | CC [M] drivers/net/can/sja1000/sja1000.o > | drivers/net/can/sja1000/sja1000.c: In function =E2=80=98sja1000_reset_i= nterrupt=E2=80=99: > | drivers/net/can/sja1000/sja1000.c:398:9: error: too few arguments to fu= nction =E2=80=98can_free_echo_skb=E2=80=99 > | 398 | can_free_echo_skb(dev, 0); > | | ^~~~~~~~~~~~~~~~~ > | In file included from include/linux/can/dev.h:22, > | from drivers/net/can/sja1000/sja1000.c:62: > | include/linux/can/skb.h:28:6: note: declared here > | 28 | void can_free_echo_skb(struct net_device *dev, unsigned int idx, > | | ^~~~~~~~~~~~~~~~~ > | >=20 > This chance is mainline since v5.13-rc1~94^2~297^2~34. I've fixed the > problem while applying the patch. I didn't, I fixed that in August and forgot I was on a 5.10 when submitting, as mainline does not run on the platform I used to test. Thanks for fixing. Miqu=C3=A8l