From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 93D0AC636CD for ; Tue, 7 Feb 2023 09:17:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231518AbjBGJRo (ORCPT ); Tue, 7 Feb 2023 04:17:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231480AbjBGJRg (ORCPT ); Tue, 7 Feb 2023 04:17:36 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C74BE38038 for ; Tue, 7 Feb 2023 01:17:34 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 36A4061241 for ; Tue, 7 Feb 2023 09:17:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A3E6C4339C; Tue, 7 Feb 2023 09:17:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1675761453; bh=i1zrv3X6r9sK/wwl6s329SagX7qc/H9TPSL57ikzERY=; h=Subject:To:Cc:From:Date:From; b=ec4LPNkUIj9Zpf7zAWjgKbC3r7Zv/OxEuuOTZ29iJwwmk3DdbF9qfQsFPH/3dOejG kvt3vwAv8EedoD6Q6/cZkqkKkyqTpn19C+ZoKK5mGgqkUOhTEhioaFc+qD30m7WVpR KaSt5LLmTfE1xw18xQ8RpT+BULtnkYQPZMWwsLag= Subject: FAILED: patch "[PATCH] serial: 8250_dma: Fix DMA Rx rearm race" failed to apply to 4.19-stable tree To: ilpo.jarvinen@linux.intel.com, gilles.buloz@kontron.com, gregkh@linuxfoundation.org Cc: From: Date: Tue, 07 Feb 2023 10:17:22 +0100 Message-ID: <167576144246113@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . Possible dependencies: 57e9af7831dc ("serial: 8250_dma: Fix DMA Rx rearm race") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 57e9af7831dcf211c5c689c2a6f209f4abdf0bce Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= Date: Mon, 30 Jan 2023 13:48:41 +0200 Subject: [PATCH] serial: 8250_dma: Fix DMA Rx rearm race MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit As DMA Rx can be completed from two places, it is possible that DMA Rx completes before DMA completion callback had a chance to complete it. Once the previous DMA Rx has been completed, a new one can be started on the next UART interrupt. The following race is possible (uart_unlock_and_check_sysrq_irqrestore() replaced with spin_unlock_irqrestore() for simplicity/clarity): CPU0 CPU1 dma_rx_complete() serial8250_handle_irq() spin_lock_irqsave(&port->lock) handle_rx_dma() serial8250_rx_dma_flush() __dma_rx_complete() dma->rx_running = 0 // Complete DMA Rx spin_unlock_irqrestore(&port->lock) serial8250_handle_irq() spin_lock_irqsave(&port->lock) handle_rx_dma() serial8250_rx_dma() dma->rx_running = 1 // Setup a new DMA Rx spin_unlock_irqrestore(&port->lock) spin_lock_irqsave(&port->lock) // sees dma->rx_running = 1 __dma_rx_complete() dma->rx_running = 0 // Incorrectly complete // running DMA Rx This race seems somewhat theoretical to occur for real but handle it correctly regardless. Check what is the DMA status before complething anything in __dma_rx_complete(). Reported-by: Gilles BULOZ Tested-by: Gilles BULOZ Fixes: 9ee4b83e51f7 ("serial: 8250: Add support for dmaengine") Cc: stable@vger.kernel.org Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20230130114841.25749-3-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c index 5594883a96f8..7fa66501792d 100644 --- a/drivers/tty/serial/8250/8250_dma.c +++ b/drivers/tty/serial/8250/8250_dma.c @@ -43,15 +43,23 @@ static void __dma_rx_complete(struct uart_8250_port *p) struct uart_8250_dma *dma = p->dma; struct tty_port *tty_port = &p->port.state->port; struct dma_tx_state state; + enum dma_status dma_status; int count; - dma->rx_running = 0; - dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state); + /* + * New DMA Rx can be started during the completion handler before it + * could acquire port's lock and it might still be ongoing. Don't to + * anything in such case. + */ + dma_status = dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state); + if (dma_status == DMA_IN_PROGRESS) + return; count = dma->rx_size - state.residue; tty_insert_flip_string(tty_port, dma->rx_buf, count); p->port.icount.rx += count; + dma->rx_running = 0; tty_flip_buffer_push(tty_port); }