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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 68958FF885D for ; Tue, 28 Apr 2026 13:07:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=tBn8VqLDSKuQcw7PUXmOHeUfy7B2aRFPY4QqUqpeL/s=; b=ZGp3/Me5o/fWG8pyk+Ny/5zMzD b7TUNxnhC6fVsc8sPx+z4FKidmaK/x8LTWKqZVldAO+zXMvV+8q5XvCuoo+gGPN1xsWoNeiY2KcYe 85rqNTz/0CCNi4NX1RgCqzuD1FIzinxorv2A6Dh2Syt8MM9geInL0563A6Kvkr+c9q4PcPZRdqo80 Gh9E5PpzT6UYdtYBo76jqeNkqp+Wt8gDAZKLj7Fqg3lbRJmBF+p16FPoFarOSIbDwuTcm82CGnL// LeMd1vRnznzcJT7Mcb0CG1RpNsphkpwSDMoLr/OAn2+/NCpq5GQaRUXaDIwgCYCcKHKQKzqZ3l//y 8IWPt2nQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wHiAJ-00000001UaG-3cXl; Tue, 28 Apr 2026 13:07:51 +0000 Received: from jpms-ob02.noc.sony.co.jp ([2001:cf8:ace:41::5]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wHiAG-00000001UZr-1wHH for linux-arm-kernel@lists.infradead.org; Tue, 28 Apr 2026 13:07:50 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sony.com; s=s1jp; t=1777381669; x=1808917669; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=tBn8VqLDSKuQcw7PUXmOHeUfy7B2aRFPY4QqUqpeL/s=; b=h8+nnWSpinkZLolHSI1DrjI29pyZX8USFdhNcfMp8U+ntfearbgDI+bW F5jTVuZ5RIl/BJtqTLPCBCSF2mEixmZysvxmzoB5qG+Bj7OdkKNZf7zWx pGrou+zUc3BLZmGm20Bw2ieLQjFqPAx6KN2MlLv/WOa3UhRecahI4e8Vy YOqSz38XGsgdJHWRDwVzyTRcLozAM5L1W0IiEwDXN08ApCIXH2BLs7QL3 RiaiSA4f/5At9umxNNdv7wcZOjGxerCUN+UJmqV9te7Kq1+nXJiINFlr1 /K8vvLhBtzEnGMyWHrMfOWs+SlT/cnJER0sLoygvY4ZB7eqbwyOAea7wA A==; X-CSE-ConnectionGUID: oDcvBipVSHuflW/pAloYiw== X-CSE-MsgGUID: xpJuB0y2TJOdlooJ8gr/HA== Received: from unknown (HELO jpmta-ob02.noc.sony.co.jp) ([IPv6:2001:cf8:0:6e7::7]) by jpms-ob02.noc.sony.co.jp with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Apr 2026 22:07:44 +0900 X-CSE-ConnectionGUID: dQXwq35VQs6FZkNfdUoPYQ== X-CSE-MsgGUID: CInvrjD1Rz2rtwWAUCwLvQ== X-IronPort-AV: E=Sophos;i="6.23,204,1770562800"; d="scan'208";a="604129736" Received: from unknown (HELO JPC00244420) ([IPv6:2001:cf8:1:573:0:dddd:eb3e:119e]) by jpmta-ob02.noc.sony.co.jp with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Apr 2026 22:07:42 +0900 Date: Tue, 28 Apr 2026 22:07:41 +0900 From: Shashank Balaji To: Gary Guo , Thierry Reding , Jonathan Hunter Cc: Suzuki K Poulose , James Clark , Alexander Shishkin , Maxime Coquelin , Alexandre Torgue , Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , Miguel Ojeda , Boqun Feng , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Richard Cochran , Jonathan Corbet , Shuah Khan , Luis Chamberlain , Petr Pavlu , Daniel Gomez , Sami Tolvanen , Aaron Tomlin , Mike Leach , Leo Yan , Rahul Bukte , linux-kernel@vger.kernel.org, coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, driver-core@lists.linux.dev, rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org, Daniel Palmer , Tim Bird , linux-modules@vger.kernel.org, linux-tegra@vger.kernel.org Subject: Re: [PATCH v4 1/4] kernel: param: initialize module_kset before do_initcalls() Message-ID: References: <20260427-acpi_mod_name-v4-0-22b42240c9bf@sony.com> <20260427-acpi_mod_name-v4-1-22b42240c9bf@sony.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260428_060748_750003_CCE3341C X-CRM114-Status: GOOD ( 30.48 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Adding Tegra maintainers. On Tue, Apr 28, 2026 at 12:10:50PM +0100, Gary Guo wrote: > On Tue Apr 28, 2026 at 1:37 AM BST, Shashank Balaji wrote: > > Hi Gary, > > > > On Mon, Apr 27, 2026 at 02:29:55PM +0100, Gary Guo wrote: > >> On Mon Apr 27, 2026 at 3:41 AM BST, Shashank Balaji wrote: > >> > module_kset is initialized in param_sysfs_init(), a subsys_initcall. A number > >> > of platform drivers register themselves prior to subsys_initcalls > >> > (tegra194_cbb_driver registers in a pure_initcall, for example). With an > >> > upcoming patch ("driver core: platform: set mod_name in driver registration") > >> > that sets their mod_name in struct device_driver, lookup_or_create_module_kobject() > >> > will be called for those drivers, which calls kset_find_obj(module_kset, mod_name). > >> > This causes a null deref because module_kset isn't alive yet. > >> > > >> > Fix this by initializing module_kset in do_basic_setup() before do_initcalls(). > >> > Modernize the pr_warn while we're at it. > >> > > >> > Suggested-by: Greg Kroah-Hartman > >> > Suggested-by: Gary Guo > >> > >> I didn't suggest this change :) > >> > >> I suggested `pure_initcall`, which is just a one line change. > > > > Oops, sorry about the misattribution. > > > >> diff --git a/kernel/params.c b/kernel/params.c > >> index 74d620bc2521..ac088d4b09a9 100644 > >> --- a/kernel/params.c > >> +++ b/kernel/params.c > >> @@ -957,7 +957,7 @@ static int __init param_sysfs_init(void) > >> > >> return 0; > >> } > >> -subsys_initcall(param_sysfs_init); > >> +pure_initcall(param_sysfs_init); > >> > >> /* > >> * param_sysfs_builtin_init - add sysfs version and parameter > >> > >> pure_initcall is level 0 so it happens before all other init calls. Does it not > >> work? > > > > tegra194_cbb_driver registers itself in a pure_initcall too. We wouldn't > > want the ordering of its registration and module_kset init to be link order > > dependent. > > It's the only device driver that does this. And I don't think it's supposed to. > > >From documentation: > > > A "pure" initcall has no dependencies on anything else, and purely > > initializes variables that couldn't be statically initialized. > > I understand that given large amount of drivers registering themselves during > core/arch_initcall that there might be regressions if all of them are moved, but > surely we can demote these two specific tegra driver to core/postcore_initcall? > This will still be called earlier than init_machine call which happens during > arch_initcall. > > Looks like the tegra CBB driver is just doing error logging anyway. That's a good point, Gary. Thanks! Hi Thierry and Jonathan, You can find the context for this email in this patch: https://lore.kernel.org/all/20260427-acpi_mod_name-v4-1-22b42240c9bf@sony.com/ TL;DR: tegra194_cbb_driver and tegra234_cbb_driver are the only drivers registering themselves as early as in a pure_initcall. This is a problem on two fronts: 1. Philosophical: As Gary pointed out, pure_initcalls are intended to purely initialize variables that couldn't be statically initialized. But these are doing driver registrations. 2. module_kset not initialized at pure_initcall stage: This is needed to set the module sysfs symlink. Since module_kset is not alive yet during pure_initcalls, registering these drivers panics the kernel. We would like to do the tegra cbb driver registration in a core_initcall (or some later initcall works too), and move module_kset initialization to a pure_initcall. Like this: diff --git a/drivers/soc/tegra/cbb/tegra194-cbb.c b/drivers/soc/tegra/cbb/tegra194-cbb.c index ab75d50cc85c..2f69e104c838 100644 --- a/drivers/soc/tegra/cbb/tegra194-cbb.c +++ b/drivers/soc/tegra/cbb/tegra194-cbb.c @@ -2342,7 +2342,7 @@ static int __init tegra194_cbb_init(void) { return platform_driver_register(&tegra194_cbb_driver); } -pure_initcall(tegra194_cbb_init); +core_initcall(tegra194_cbb_init); static void __exit tegra194_cbb_exit(void) { diff --git a/drivers/soc/tegra/cbb/tegra234-cbb.c b/drivers/soc/tegra/cbb/tegra234-cbb.c index fb26f085f691..785072fa4e85 100644 --- a/drivers/soc/tegra/cbb/tegra234-cbb.c +++ b/drivers/soc/tegra/cbb/tegra234-cbb.c @@ -1774,7 +1774,7 @@ static int __init tegra234_cbb_init(void) { return platform_driver_register(&tegra234_cbb_driver); } -pure_initcall(tegra234_cbb_init); +core_initcall(tegra234_cbb_init); static void __exit tegra234_cbb_exit(void) { Would this work? Thanks, Shashank