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 C9F5430F94 for ; Thu, 28 Sep 2023 07:53:30 +0000 (UTC) Received: from metis.whiteo.stw.pengutronix.de (metis.whiteo.stw.pengutronix.de [IPv6:2a0a:edc0:2:b01:1d::104]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A2C17C1 for ; Thu, 28 Sep 2023 00:53:28 -0700 (PDT) Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1qllpn-0001KQ-JF; Thu, 28 Sep 2023 09:53:19 +0200 Received: from [2a0a:edc0:0:b01:1d::7b] (helo=bjornoya.blackshift.org) by drehscheibe.grey.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1qllpm-009WkC-In; Thu, 28 Sep 2023 09:53:18 +0200 Received: from pengutronix.de (unknown [172.20.34.65]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) (Authenticated sender: mkl-all@blackshift.org) by smtp.blackshift.org (Postfix) with ESMTPSA id 2CBB322A28F; Thu, 28 Sep 2023 07:53:18 +0000 (UTC) Date: Thu, 28 Sep 2023 09:53:17 +0200 From: Marc Kleine-Budde To: Miquel Raynal 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 v2] can: sja1000: Always restart the Tx queue after an overrun Message-ID: <20230928-headphone-premiere-d92deb9c29e5-mkl@pengutronix.de> References: <20230927164442.128204-1-miquel.raynal@bootlin.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="ubhnszgeqgcjawt6" Content-Disposition: inline In-Reply-To: <20230927164442.128204-1-miquel.raynal@bootlin.com> X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.whiteo.stw.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: netdev@vger.kernel.org X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_LOW, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net --ubhnszgeqgcjawt6 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 27.09.2023 18:44:42, 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. 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 re= set on Renesas SoCs") > Cc: stable@vger.kernel.org > Signed-off-by: Miquel Raynal > --- >=20 > Changes in v2: > * As Marc sugested, use netif_tx_{,un}lock() instead of our own > spin_lock. >=20 > drivers/net/can/sja1000/sja1000.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) >=20 > diff --git a/drivers/net/can/sja1000/sja1000.c b/drivers/net/can/sja1000/= sja1000.c > index ae47fc72aa96..91e3fb3eed20 100644 > --- a/drivers/net/can/sja1000/sja1000.c > +++ b/drivers/net/can/sja1000/sja1000.c > @@ -297,6 +297,7 @@ static netdev_tx_t sja1000_start_xmit(struct sk_buff = *skb, > if (can_dropped_invalid_skb(dev, skb)) > return NETDEV_TX_OK; > =20 > + netif_tx_lock(dev); > netif_stop_queue(dev); > =20 > fi =3D dlc =3D cf->can_dlc; > @@ -335,6 +336,8 @@ static netdev_tx_t sja1000_start_xmit(struct sk_buff = *skb, > =20 > sja1000_write_cmdreg(priv, cmd_reg_val); > =20 > + netif_tx_unlock(dev); > + I think netif_tx_lock() should be used in a different way. As far as I understand it, you should call it only in the sja1000_reset_interrupt(), where you want to tx path to interfere. Please test the new code with lockdep enabled. Marc > return NETDEV_TX_OK; > } > =20 > @@ -396,7 +399,13 @@ static irqreturn_t sja1000_reset_interrupt(int irq, = void *dev_id) > struct net_device *dev =3D (struct net_device *)dev_id; > =20 > netdev_dbg(dev, "performing a soft reset upon overrun\n"); > - sja1000_start(dev); > + > + netif_tx_lock(dev); > + > + can_free_echo_skb(dev, 0); > + sja1000_set_mode(dev, CAN_MODE_START); > + > + netif_tx_unlock(dev); > =20 > return IRQ_HANDLED; > } > --=20 > 2.34.1 >=20 >=20 --=20 Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung N=C3=BCrnberg | Phone: +49-5121-206917-129 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-9 | --ubhnszgeqgcjawt6 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEDs2BvajyNKlf9TJQvlAcSiqKBOgFAmUVMOoACgkQvlAcSiqK BOglxgf+Kwi7Em2vSA6/cuQGPluAhGuXsyUHgOY0hkuRW47y63FhXrkUTylD0/Jy Bf5WX2gm+fFQZvo3BJphPalQq7pQopv4ewDBKBC1wtRWFSqQqaFS86eIzQ2su19f Ox9QliSCS6QI91K+5eZguv0FnsHn48mDe076NpLUrERsQjb0M9ocxjeNChknqk+3 JZQILGjmF/moHS8oISZj6YCQ8dj/EnBZVieKJFWHunbxqep2Q9U/j897apUjOGXr N1Okes5SIA+ou51FxRgR/jhywyZUIjyMN0uNc3K5lufHQHKBt0GKqyTIZCzrYd+X maJNukSC0G55y55Gx2ZkNC4iO2mljQ== =Pj/g -----END PGP SIGNATURE----- --ubhnszgeqgcjawt6--