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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 A5E06C432C3 for ; Sun, 24 Nov 2019 15:44:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 79A3D2075E for ; Sun, 24 Nov 2019 15:44:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="gcN26IH2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726680AbfKXPn7 (ORCPT ); Sun, 24 Nov 2019 10:43:59 -0500 Received: from mail-yb1-f194.google.com ([209.85.219.194]:37965 "EHLO mail-yb1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725989AbfKXPn7 (ORCPT ); Sun, 24 Nov 2019 10:43:59 -0500 Received: by mail-yb1-f194.google.com with SMTP id k206so4987119ybb.5 for ; Sun, 24 Nov 2019 07:43:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id; bh=7GoVKZppoRs4H8MV5EKljB+lt4NwFU2QYQ4kHf9aeFM=; b=gcN26IH29ommNyDhhBdS4LUjBSrhnXAY5ZK1+Yfk+Ut2ikTr3yycJPIH/+RCBpTxej N3TJayJ955EbCu045tGM2rEeL1myhqCn4BIxYOU16q0Shyq0hjbSHBw/MRfXxxVnzG2a hoiIRe8KalUW2+Fl4zEqdIbGYkOibTEl4kdeDcDIM9ExUeU8to+bnMXaGRqKOFlooUmy OWxikAkr9yZ/fEAc3KUdjeUrD7Tzb78Z4PkiftSuvzZAtAvNtPDacWCgA+Kyxle6eoo2 H4tCC/DHHg6AbTdmSWPMpy8WHZHMZBfOfC2TZhYTLcO3OoW0VYxhjd/iz+a8H9oY7niu m3XA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=7GoVKZppoRs4H8MV5EKljB+lt4NwFU2QYQ4kHf9aeFM=; b=OHrfAnRh6FsTztdjjugMZs83l9XMwhTNQP/sSTS0q2Tp3MUQm3yVI3/Oa8hjA5fQfQ TpbTj32DlS5WvUQfKFj+/l0DHOfn5PDeKunPQX99Hfhi2fy5i+Lwf3W+TnvEh+5EcFXT FQU7RNCD4+v5pvC8xvCg6pf/MEa5QY+dZQNJhDFHSC9lqv83KpauSUalQMjEWvXIlyn+ 3R1qQBeHMpY1Cs2hfLB0SLOHW7pXWW5fk9Stq7u7HlFExA7uDFzaG11knvuVymhgEFIM NV8vq9n1+ALEDVQeVkzqxvCYwkW2/7Eis9/oSrbjA764rd9bkQ91Mn50WhYOpSbuwrm+ cggg== X-Gm-Message-State: APjAAAW6UTRosFyNTMOkk3X1QcQGdeg17WlXj5YjzxG2Ru+Vd/7Dt41k Q1ounj/IXDmxC9PIxNNeYuU5aQ== X-Google-Smtp-Source: APXvYqyEZRjk614ciccDP+789BFWvngD1xEZFN1RKPsZLP+LMRQQPwNkhHtc3XCbgw+xJQsROxYehg== X-Received: by 2002:a25:8281:: with SMTP id r1mr19218080ybk.489.1574610237279; Sun, 24 Nov 2019 07:43:57 -0800 (PST) Received: from localhost.localdomain (li2093-158.members.linode.com. [172.105.159.158]) by smtp.gmail.com with ESMTPSA id h81sm2222564ywa.78.2019.11.24.07.43.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 24 Nov 2019 07:43:56 -0800 (PST) From: Leo Yan To: Andy Gross , Greg Kroah-Hartman , Jiri Slaby , Bjorn Andersson , Stephen Boyd , Nicolas Dechesne , linux-arm-msm@vger.kernel.org, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Leo Yan Subject: [PATCH 1/2] tty: serial: msm_serial: Fix lockup for sysrq and oops Date: Sun, 24 Nov 2019 23:43:33 +0800 Message-Id: <20191124154334.15366-1-leo.yan@linaro.org> X-Mailer: git-send-email 2.17.1 Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org 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. Signed-off-by: Leo Yan --- drivers/tty/serial/msm_serial.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c index 3657a24913fc..889538182e83 100644 --- a/drivers/tty/serial/msm_serial.c +++ b/drivers/tty/serial/msm_serial.c @@ -1576,6 +1576,7 @@ static void __msm_console_write(struct uart_port *port, const char *s, int num_newlines = 0; bool replaced = false; void __iomem *tf; + int locked = 1; if (is_uartdm) tf = port->membase + UARTDM_TF; @@ -1588,7 +1589,13 @@ static void __msm_console_write(struct uart_port *port, const char *s, 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); @@ -1624,7 +1631,9 @@ static void __msm_console_write(struct uart_port *port, const char *s, 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, -- 2.17.1