From patchwork Tue Jan 7 20:55:24 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 234358 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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham 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 4DC39C33C9B for ; Tue, 7 Jan 2020 21:10:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 217B92080A for ; Tue, 7 Jan 2020 21:10:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578431457; bh=JewF3hFRuX/PkV+WWKtCR2vi4s3Yk9cy/ML2nD4xAf0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ErtfmsRyTPGI5VqvojfSbkjj0pVbBayPs8hlab4TNGpj6jCTzfJ9upeXyBpSY4KoB zAPjN4offFQu81f/gR3vKcY3Imp/B2F28Q/GC6yeBXpQ5gOJTatTDhLb6KEoGQogey Yn9xVkb3PPhsRFlZ7qJw/BELfu6kx/6JJF89YU6M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730032AbgAGVK4 (ORCPT ); Tue, 7 Jan 2020 16:10:56 -0500 Received: from mail.kernel.org ([198.145.29.99]:37834 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730010AbgAGVKr (ORCPT ); Tue, 7 Jan 2020 16:10:47 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5CD752072A; Tue, 7 Jan 2020 21:10:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578431446; bh=JewF3hFRuX/PkV+WWKtCR2vi4s3Yk9cy/ML2nD4xAf0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Or21Lqc1ST+66x0wGb0XoXj1j/3jtUJRSQYmiCWbpKtEqSTdiEJQeEqqFtUSM7/wX 0vR3t0gU0q8YSlQNQn++LfcxemOAG9/QQCwxmfmrpfA4UdxQV9crpGxJazC6Zn2vVI nHQNO82nCAZ15zYNVTkEhuynBqiQz2YQdeLQaB8M= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Leo Yan , Jeffrey Hugo Subject: [PATCH 4.14 59/74] tty: serial: msm_serial: Fix lockup for sysrq and oops Date: Tue, 7 Jan 2020 21:55:24 +0100 Message-Id: <20200107205224.160680969@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200107205135.369001641@linuxfoundation.org> References: <20200107205135.369001641@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Leo Yan commit 0e4f7f920a5c6bfe5e851e989f27b35a0cc7fb7e upstream. As the commit 677fe555cbfb ("serial: imx: Fix recursive locking bug") has mentioned the uart driver might cause recursive locking between normal printing and the kernel debugging facilities (e.g. sysrq and oops). In the commit it gave out suggestion for fixing recursive locking issue: "The solution is to avoid locking in the sysrq case and trylock in the oops_in_progress case." This patch follows the suggestion (also used the exactly same code with other serial drivers, e.g. amba-pl011.c) to fix the recursive locking issue, this can avoid stuck caused by deadlock and print out log for sysrq and oops. Fixes: 04896a77a97b ("msm_serial: serial driver for MSM7K onboard serial peripheral.") Signed-off-by: Leo Yan Reviewed-by: Jeffrey Hugo Link: https://lore.kernel.org/r/20191127141544.4277-2-leo.yan@linaro.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/msm_serial.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) --- a/drivers/tty/serial/msm_serial.c +++ b/drivers/tty/serial/msm_serial.c @@ -1588,6 +1588,7 @@ static void __msm_console_write(struct u int num_newlines = 0; bool replaced = false; void __iomem *tf; + int locked = 1; if (is_uartdm) tf = port->membase + UARTDM_TF; @@ -1600,7 +1601,13 @@ static void __msm_console_write(struct u num_newlines++; count += num_newlines; - spin_lock(&port->lock); + if (port->sysrq) + locked = 0; + else if (oops_in_progress) + locked = spin_trylock(&port->lock); + else + spin_lock(&port->lock); + if (is_uartdm) msm_reset_dm_count(port, count); @@ -1636,7 +1643,9 @@ static void __msm_console_write(struct u iowrite32_rep(tf, buf, 1); i += num_chars; } - spin_unlock(&port->lock); + + if (locked) + spin_unlock(&port->lock); } static void msm_console_write(struct console *co, const char *s,