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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 4B9F8C433E0 for ; Wed, 6 Jan 2021 09:29:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EEE9A23102 for ; Wed, 6 Jan 2021 09:29:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726493AbhAFJ3m (ORCPT ); Wed, 6 Jan 2021 04:29:42 -0500 Received: from szxga07-in.huawei.com ([45.249.212.35]:10394 "EHLO szxga07-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726249AbhAFJ3l (ORCPT ); Wed, 6 Jan 2021 04:29:41 -0500 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4D9kYc73G9z7PnK; Wed, 6 Jan 2021 17:28:04 +0800 (CST) Received: from [10.136.114.193] (10.136.114.193) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.498.0; Wed, 6 Jan 2021 17:28:52 +0800 Subject: Re: [PATCH] tty/serial/8250: make touch watchdog settable To: Sergey Senozhatsky CC: , , , , , , , References: <20210106064641.2621838-1-chenzhen105@huawei.com> From: "chenzhen (R)" Message-ID: Date: Wed, 6 Jan 2021 17:28:57 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.136.114.193] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/1/6 15:33, Sergey Senozhatsky wrote: > On (21/01/06 14:46), chenzhen wrote: >> Since 54f19b4a6(tty/serial/8250: Touch NMI watchdog in wait_for_xmitr), serial8250 >> will always touch watchdog in write and wait_for_xmitr. However, serial8250 may >> become low speed thus take a long time to print. In this process, nmi and soft >> watchdog on current CPU will be invalid. >> >> To resolve this problem, add a cmdline option "tty_watchdog_enable" to control >> the touchdog in serial8250. > Sorry, I don't understand - what does this fix? > > -ss > . It fixes that if serial8250 is low speed on some machine, when it writes for a long time, NMI/softlockup watchdog will never bark and potential rlock will not be detected. So an option to control the touchdog in serial8250 may help. Thanks for your reply!                                                                  -Zhen Chen