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 1FA6FC4167D for ; Mon, 7 Feb 2022 07:00:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241125AbiBGG6Y (ORCPT ); Mon, 7 Feb 2022 01:58:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353653AbiBGGhw (ORCPT ); Mon, 7 Feb 2022 01:37:52 -0500 Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A44AAC043181; Sun, 6 Feb 2022 22:37:50 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R121e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01424;MF=xuyu@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0V3mOTeH_1644215867; Received: from 30.225.28.93(mailfrom:xuyu@linux.alibaba.com fp:SMTPD_---0V3mOTeH_1644215867) by smtp.aliyun-inc.com(127.0.0.1); Mon, 07 Feb 2022 14:37:47 +0800 Message-ID: Date: Mon, 7 Feb 2022 14:37:46 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.5.1 Subject: Re: [PATCH] chardev: call tty_init() in real chrdev_init() Content-Language: en-US To: Greg KH Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, arnd@arndb.de, viro@zeniv.linux.org.uk, dhowells@redhat.com References: <4e753e51d0516413fbf557cf861d654ca73486cc.1644164597.git.xuyu@linux.alibaba.com> From: Yu Xu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/7/22 1:03 AM, Greg KH wrote: > On Mon, Feb 07, 2022 at 12:27:31AM +0800, Xu Yu wrote: >> It is confusing that tty_init() in called in the initialization of >> memdev, i.e., static chr_dev_init(). >> >> Through blame, it is introduced by commit 31d1d48e199e ("Fix init >> ordering of /dev/console vs callers of modprobe"), which fixes the >> initialization order of /dev/console driver. However, there seems >> to be a typo in the patch, i.e., chrdev_init, instead of chr_dev_init. >> >> This fixes the typo, IIUC. >> >> Note that the return value of tty_init() is always 0, and thus no error >> handling is provided in chrdev_init(). >> >> Fixes: 31d1d48e199e ("Fix init ordering of /dev/console vs callers of modprobe") >> Signed-off-by: Xu Yu >> --- >> drivers/char/mem.c | 2 +- >> fs/char_dev.c | 1 + >> 2 files changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/char/mem.c b/drivers/char/mem.c >> index cc296f0823bd..8c90881f8115 100644 >> --- a/drivers/char/mem.c >> +++ b/drivers/char/mem.c >> @@ -775,7 +775,7 @@ static int __init chr_dev_init(void) >> NULL, devlist[minor].name); >> } >> >> - return tty_init(); >> + return 0; >> } >> >> fs_initcall(chr_dev_init); >> diff --git a/fs/char_dev.c b/fs/char_dev.c >> index ba0ded7842a7..fc042a0a098f 100644 >> --- a/fs/char_dev.c >> +++ b/fs/char_dev.c >> @@ -667,6 +667,7 @@ static struct kobject *base_probe(dev_t dev, int *part, void *data) >> void __init chrdev_init(void) >> { >> cdev_map = kobj_map_init(base_probe, &chrdevs_lock); >> + tty_init(); >> } >> > > You just changed the ordering sequence here, are you SURE this is > correct? To be honest, not 100% sure. > > How was this tested? Did you verify that the problem that the original > commit here was fixing is now not happening again? I tried to reproduce the issue described in the original commit, and failed. The issue does not appear, or my reproduction is wrong. 1. revert 31d1d48e199e manually; 2. request_module("xxx") anywhere before do_initcalls(), since tty_init() now is initialized by module_init(); 3. no warning on request_module is shown. > > And what real problem is this solving? How did you hit the issue that > this solves? No real problem actually. As described in the log, it is confusing that tty_init() in called in the initialization of memdev. They don't have strong dependencies. I found the issue when I read through codes of drivers/char/mem.c. > > And finally, yes, it is not good to throw away the return value of > tty_init(). If it really can not return anything but 0, then let us > make it a void function first. Got it. But I will first try to figure out whether this patch is a real issue. > > thanks, > > greg k-h -- Thanks, Yu