From nobody Mon Nov 25 11:42:15 2024 Received: from mail-wm1-f53.google.com (mail-wm1-f53.google.com [209.85.128.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 310961DFE1E for ; Mon, 28 Oct 2024 16:46:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.53 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730133966; cv=none; b=slbJFr/P1yK2jGxLRGXgGX2pWukZI+GGZ6CYQmQ5ikMJGJW5Ylyc8E8dnKXFbSZMlhP6aPRAyo365TnxBLEYaBcRpB64dCnjNGhkoWSwr8lCAOxj+HXLsWcUYNSoE6teuILznos3UqHY7QQkx/nwqYbqXWWeABr0tPtOahUo600= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730133966; c=relaxed/simple; bh=sI52s5i9k4pYNrQHBS72EU98OIueE15hSE4KEthCY5Y=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=qGb41gKVFC5Fv3DFh9qGDOtw8INuok4WjW+w/7pbqc2dw5EMBBJoAnpPCWCn2jDD3tzY7GKQGw4770G5uP6/KFEnpm+CVpXefwUoU80mf9Tk4bOoXOLmZEl0tEBsN4Pkw6UTyZcWeBLfYyuWUBixKnir9iDeSIVksHwr0c8ac+Y= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=chrisdown.name; spf=pass smtp.mailfrom=chrisdown.name; dkim=pass (1024-bit key) header.d=chrisdown.name header.i=@chrisdown.name header.b=Yy/MUa9l; arc=none smtp.client-ip=209.85.128.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=chrisdown.name Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chrisdown.name Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chrisdown.name header.i=@chrisdown.name header.b="Yy/MUa9l" Received: by mail-wm1-f53.google.com with SMTP id 5b1f17b1804b1-431ac30d379so9160745e9.1 for ; Mon, 28 Oct 2024 09:46:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chrisdown.name; s=google; t=1730133960; x=1730738760; darn=vger.kernel.org; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=NbATi4LQJSIUmiSf9Q8b/uDqq/jBD5xLfukP+H/32dM=; b=Yy/MUa9l2q67eBZtZoYV0tINKz0i/IlLmYxLOGmiK4a+F2budkEVrzG4skhk8MpVqr ScMrw8XKmBfcylZpPbk8JaQuXMElpCcbfNHjchLe64PoxfGM7loU8NZ7qiukRH/Wr8ZI iK+hKFmHFjkGaESjIaUf13tCUG6FGx+uuAkCM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1730133960; x=1730738760; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=NbATi4LQJSIUmiSf9Q8b/uDqq/jBD5xLfukP+H/32dM=; b=Q9AqS0Ws8246t+RD1M7f+OEQuGb2mKyH9jvhZ5llh4/x3lGVQwcQYDR3YnC4Tw9ip7 pC9Lse5YPO/zKl2u1+aMCHBLnzG/xVu7nytqY9QzRocNdYPDI32xkMItb3T2nemm90PX HID/JvaiX9p0zKvLLMKqA8dE2/7PSQA/ci4+l10gCC5RZLiguTG+M8cTz/Ea/g2wYvTy ZeqlY9cojfogbbv9WPWcGz6YyjoLPlaiLEznndnaB4fIkjzvlGzhbLT5x8wjldvnWnOz trFyuat7/PD2gdrxZFdailrBQwzJoJATYqPFrHVwRGECL9HJuLQnmRtoiuUonr7O3Rw/ Jhvg== X-Gm-Message-State: AOJu0YxspVcIUInjBjkceY1gk4VsDACdTqpM0/PysTiwF5e8w2BhtBXQ haGW9zgWgHVjiIujD0MQp7/W9V4EwJxR6ILqN4lpoJ557BtdH3bQ1g42us7FMHA= X-Google-Smtp-Source: AGHT+IEvvpnLREHjelMIBqHzAmiYJ5zM0d1BpPVE3JPzD4+dRIX/DKHK7f23k+8pfDQQZhz5g38RgQ== X-Received: by 2002:a05:600c:4e8b:b0:431:40ca:ce44 with SMTP id 5b1f17b1804b1-4319ad34a44mr68787325e9.30.1730133960493; Mon, 28 Oct 2024 09:46:00 -0700 (PDT) Received: from localhost ([93.115.193.42]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38058b929a8sm10083304f8f.103.2024.10.28.09.45.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Oct 2024 09:46:00 -0700 (PDT) Date: Mon, 28 Oct 2024 16:45:59 +0000 From: Chris Down To: Petr Mladek Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Sergey Senozhatsky , Steven Rostedt , John Ogness , Geert Uytterhoeven , Tony Lindgren , kernel-team@fb.com Subject: [PATCH v6 10/11] printk: Deprecate the kernel.printk sysctl interface Message-ID: <993d978d4a59dd370ac39c6c24c9b72c11f4dc74.1730133890.git.chris@chrisdown.name> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.13 (00d56288) (2024-03-09) Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The kernel.printk sysctl interface is deprecated in favour of more granular and clearer sysctl interfaces for controlling loglevels, namely kernel.console_loglevel and kernel.default_message_loglevel. kernel.printk has a number of fairly significant usability problems: - It takes four values in a specific order, which is not intuitive. Speaking from personal experience, even people working on printk sometimes need to look up the order of these values, which doesn't suggest much in the way of perspicuity. - There is no validation on the input values, so users can set them to invalid or nonsensical values without receiving any errors or warnings. This can lead to unpredictable behaviour. - One of the four values, default_console_loglevel, is not used in the kernel (see below), making it redundant and potentially confusing. - Overall, the interface is complex, hard to understand, and combines multiple controls into a single sysctl, which is not ideal. It should be separated into distinct controls for clarity. Setting kernel.printk now calls printk_sysctl_deprecated, which emits a pr_warn. The warning informs users about the deprecation and suggests using the new sysctl interfaces instead. By deprecating kernel.printk, we aim to: - Encourage users to adopt the new, dedicated sysctl interfaces (kernel.console_loglevel and kernel.default_message_loglevel), which are more straightforward and easier to understand. - Improve input validation and error handling, ensuring that users receive appropriate feedback when setting invalid values. - Simplify the configuration of loglevels by exposing only the controls that are necessary and relevant. Signed-off-by: Chris Down Reviewed-by: Petr Mladek --- Documentation/admin-guide/sysctl/kernel.rst | 3 +++ kernel/printk/sysctl.c | 14 +++++++++++++- 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/ad= min-guide/sysctl/kernel.rst index 8019779b27f6..6027f0057ea3 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -1061,6 +1061,9 @@ Messages without an explicit priority will be printed= with this priority. printk =3D=3D=3D=3D=3D=3D =20 +This sysctl is deprecated and will be removed in future. Please consider u= sing +``kernel.console_loglevel`` or ``kernel.default_message_loglevel`` instead. + The four values in printk denote: ``console_loglevel``, ``default_message_loglevel``, ``minimum_console_loglevel`` and ``default_console_loglevel`` respectively. diff --git a/kernel/printk/sysctl.c b/kernel/printk/sysctl.c index 3bce8b89dacc..42f9e94b1e47 100644 --- a/kernel/printk/sysctl.c +++ b/kernel/printk/sysctl.c @@ -7,6 +7,7 @@ #include #include #include +#include #include "internal.h" =20 static const int ten_thousand =3D 10000; @@ -46,13 +47,24 @@ static int printk_console_loglevel(const struct ctl_tab= le *table, int write, return 0; } =20 +static int printk_sysctl_deprecated(const struct ctl_table *table, int wri= te, + void *buffer, size_t *lenp, loff_t *ppos) +{ + int res =3D proc_dointvec(table, write, buffer, lenp, ppos); + + if (write) + pr_warn_once("printk: The kernel.printk sysctl is deprecated. Consider u= sing kernel.console_loglevel or kernel.default_message_loglevel instead.\n"= ); + + return res; +} + static struct ctl_table printk_sysctls[] =3D { { .procname =3D "printk", .data =3D &console_loglevel, .maxlen =3D 4*sizeof(int), .mode =3D 0644, - .proc_handler =3D proc_dointvec, + .proc_handler =3D printk_sysctl_deprecated, }, { .procname =3D "printk_ratelimit", --=20 2.46.0