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 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=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 87C24C33C9E for ; Sat, 11 Jan 2020 10:01:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5C6AB2077C for ; Sat, 11 Jan 2020 10:01:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578736897; bh=+eCP+1RMX52ZH6Ze/sdrtcDWgKk8QJnkn9Btzvb6h10=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=pILlW2Ovw/evwVZjgSrAe6WLmwOu33GjoKJLMXgEkXwkFvX7uMsL0YTIU9WIFQml+ I80qlBWuz9DD0ZME6Ozna7DXQeEHjIPS2kyydH8Yp6SfwbzfP8EVXVFSu+mqzteJtN 9lkVR24UkYr1DLa5uEAwO8bSXAp9J2b2IP5X0Q4U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729425AbgAKKBg (ORCPT ); Sat, 11 Jan 2020 05:01:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:59000 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729143AbgAKKBd (ORCPT ); Sat, 11 Jan 2020 05:01:33 -0500 Received: from localhost (unknown [62.119.166.9]) (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 0293820842; Sat, 11 Jan 2020 10:01:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578736893; bh=+eCP+1RMX52ZH6Ze/sdrtcDWgKk8QJnkn9Btzvb6h10=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zxzkfUWz+b+2Byi08AVIXreVsHgdVp8ZoL6gsfH0jMrNuo8scbfk61UtC2vmZjJ/A aWA/Rmd0FsrQCI6mQ8Kv4VqfSe3ao7RjmgYLpgL3UEZz+tGOqQgcfo48hxDQ31dslQ zoEcUIRtNGfw5huqASd3KCJCQvcF31EDhNEFEkw0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Leo Yan , Jeffrey Hugo Subject: [PATCH 4.9 43/91] tty: serial: msm_serial: Fix lockup for sysrq and oops Date: Sat, 11 Jan 2020 10:49:36 +0100 Message-Id: <20200111094901.413283246@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200111094844.748507863@linuxfoundation.org> References: <20200111094844.748507863@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 @@ -1579,6 +1579,7 @@ 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; @@ -1591,7 +1592,13 @@ 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); @@ -1627,7 +1634,9 @@ 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,