From patchwork Thu Jan 7 10:34:48 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Kleine-Budde X-Patchwork-Id: 12003509 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EBAC1C433E6 for ; Thu, 7 Jan 2021 10:35:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A782A2312F for ; Thu, 7 Jan 2021 10:35:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727451AbhAGKfm (ORCPT ); Thu, 7 Jan 2021 05:35:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726371AbhAGKfl (ORCPT ); Thu, 7 Jan 2021 05:35:41 -0500 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2167BC0612F8 for ; Thu, 7 Jan 2021 02:35:01 -0800 (PST) Received: from gallifrey.ext.pengutronix.de ([2001:67c:670:201:5054:ff:fe8d:eefb] helo=bjornoya.blackshift.org) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kxSd9-0008Q1-KI for netdev@vger.kernel.org; Thu, 07 Jan 2021 11:34:59 +0100 Received: from dspam.blackshift.org (localhost [127.0.0.1]) by bjornoya.blackshift.org (Postfix) with SMTP id E01725BBC9D for ; Thu, 7 Jan 2021 10:34:55 +0000 (UTC) Received: from hardanger.blackshift.org (unknown [172.20.34.65]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by bjornoya.blackshift.org (Postfix) with ESMTPS id 6538A5BBC80; Thu, 7 Jan 2021 10:34:53 +0000 (UTC) Received: from blackshift.org (localhost [::1]) by hardanger.blackshift.org (OpenSMTPD) with ESMTP id ef69317f; Thu, 7 Jan 2021 10:34:52 +0000 (UTC) From: Marc Kleine-Budde To: netdev@vger.kernel.org Cc: davem@davemloft.net, kuba@kernel.org, linux-can@vger.kernel.org, kernel@pengutronix.de, Marc Kleine-Budde Subject: [net 3/6] can: mcp251xfd: mcp251xfd_handle_tefif(): fix TEF vs. TX race condition Date: Thu, 7 Jan 2021 11:34:48 +0100 Message-Id: <20210107103451.183477-4-mkl@pengutronix.de> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210107103451.183477-1-mkl@pengutronix.de> References: <20210107103451.183477-1-mkl@pengutronix.de> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2001:67c:670:201:5054:ff:fe8d:eefb X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: netdev@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org The mcp251xfd driver uses a TX FIFO for sending CAN frames and a TX Event FIFO (TEF) for completed TX-requests. The TEF event handling in the mcp251xfd_handle_tefif() function has a race condition. It first increments the tx-ring's tail counter to signal that there's room in the TX and TEF FIFO, then it increments the TEF FIFO in hardware. A running mcp251xfd_start_xmit() on a different CPU might not stop the txqueue (as the tx-ring still shows free space). The next mcp251xfd_start_xmit() will push a message into the chip and the TX complete event might overflow the TEF FIFO. This patch changes the order to fix the problem. Fixes: 68c0c1c7f966 ("can: mcp251xfd: tef-path: reduce number of SPI core requests to set UINC bit") Link: https://lore.kernel.org/r/20210105214138.3150886-2-mkl@pengutronix.de Signed-off-by: Marc Kleine-Budde --- drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c index 77129d5f410b..85a1a8b7c0e7 100644 --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c @@ -1368,13 +1368,10 @@ static int mcp251xfd_handle_tefif(struct mcp251xfd_priv *priv) struct mcp251xfd_tx_ring *tx_ring = priv->tx; struct spi_transfer *last_xfer; - tx_ring->tail += len; - /* Increment the TEF FIFO tail pointer 'len' times in * a single SPI message. - */ - - /* Note: + * + * Note: * * "cs_change == 1" on the last transfer results in an * active chip select after the complete SPI @@ -1391,6 +1388,8 @@ static int mcp251xfd_handle_tefif(struct mcp251xfd_priv *priv) if (err) return err; + tx_ring->tail += len; + err = mcp251xfd_check_tef_tail(priv); if (err) return err;