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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 A2D7FC433DB for ; Mon, 28 Dec 2020 18:16:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5BC9B2242A for ; Mon, 28 Dec 2020 18:16:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728262AbgL1SQc (ORCPT ); Mon, 28 Dec 2020 13:16:32 -0500 Received: from mail.skyhub.de ([5.9.137.197]:33520 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727310AbgL1SQb (ORCPT ); Mon, 28 Dec 2020 13:16:31 -0500 Received: from zn.tnic (p200300ec2f07e40085f47ee5beeb4d19.dip0.t-ipconnect.de [IPv6:2003:ec:2f07:e400:85f4:7ee5:beeb:4d19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 0EAA41EC04D6; Mon, 28 Dec 2020 19:15:49 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1609179349; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=wufwo2Z1o8oLZgQjB0PcZyvWpV/HYOrROkTn2ihjfXE=; b=AcxBaZ/AKQVDO1bLBZsUp74HQWVJnSRjpxJ/xemieNETVVok20ec8HQC/akU8cmnvHQETu D19Mw96Mdln8K4ke52tOAK45lrrtH79y8Ka3qc12cfE5YimQHPzydpNLjtNFKqQGGWtN59 mUwg5oR39w6b3JxDFItZybX2D8vhvJg= Date: Mon, 28 Dec 2020 19:15:44 +0100 From: Borislav Petkov To: Sean Christopherson Cc: Jonathan Corbet , x86-ml , lkml Subject: Re: [PATCH] Documentation/submitting-patches: Add blurb about backtraces in commit messages Message-ID: <20201228181544.GA20321@zn.tnic> References: <20201217183756.GE23634@zn.tnic> <20201221095425.6da68163@lwn.net> <20201222130555.GA13463@zn.tnic> <20201222192517.GE13463@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 28, 2020 at 09:59:48AM -0800, Sean Christopherson wrote: > Obvious and superfluous for people that are intimately familiar with the code, > but explicit call stacks are extremely helpful when (re)learning code. Here's an example: [ 2.649874] x86/mm: Checked W+X mappings: passed, no W+X pages found. [ 2.651774] ------------[ cut here ]------------ [ 2.652726] WARNING: CPU: 2 PID: 1 at init/main.c:1436 kernel_init+0x58/0x107 [ 2.653643] Modules linked in: [ 2.654260] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.11.0-rc1+ #2 [ 2.654396] usb 1-1: new full-speed USB device number 2 using uhci_hcd [ 2.655125] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014 [ 2.657687] RIP: 0010:kernel_init+0x58/0x107 [ 2.658391] Code: 5e fc ff eb 0c 48 c7 c7 18 bc 09 82 e8 8a a4 fc ff c7 05 a2 5f b0 07 02 00 00 00 e8 a9 1c 9b ff e8 b4 dc 89 ff e8 2f d3 a6 ff <0f> 0b 48 8b 3d 76 87 9d 00 48 85 ff 74 22 e8 ef 19 fc ff 85 c0 89 [ 2.660707] RSP: 0018:ffffc90000013f50 EFLAGS: 00010292 [ 2.661499] RAX: ffff88800ebcdc01 RBX: ffffffff81837b59 RCX: 0000000000000802 [ 2.662469] RDX: 00000000000007f2 RSI: 05b5d427c1a6d18d RDI: 000000000002d100 [ 2.663411] RBP: 0000000000000000 R08: 000000000000000d R09: 000000000000000c [ 2.664318] R10: 000000000000000d R11: 0000000000000020 R12: 0000000000000000 [ 2.666458] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 2.667462] FS: 0000000000000000(0000) GS:ffff88807da80000(0000) knlGS:0000000000000000 [ 2.668472] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 2.669257] CR2: 0000000000000000 CR3: 000000000220a000 CR4: 00000000003506e0 [ 2.670183] Call Trace: [ 2.670723] ret_from_fork+0x22/0x30 [ 2.671340] ---[ end trace 385e10f347736cf9 ]--- Yes, useless. The callstack is not even there. This is the only line that matters: [ 2.652726] WARNING: CPU: 2 PID: 1 at init/main.c:1436 kernel_init+0x58/0x107 because what caused it is: diff --git a/init/main.c b/init/main.c index 6feee7f11eaf..aa52355d98ae 100644 --- a/init/main.c +++ b/init/main.c @@ -1433,6 +1433,8 @@ static int __ref kernel_init(void *unused) do_sysctl_args(); + WARN_ON_ONCE(1); + if (ramdisk_execute_command) { ret = run_init_process(ramdisk_execute_command); if (!ret) even if you had a stack trace here, it would be totally useless because you *know* where it came from. But ok, I can change the formulation that it is up to the committer's judgement to decide whether to remove that blurb. Because I definitely will be removing a useless noise like that before committing. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette