From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from jpms-ob02.noc.sony.co.jp (jpms-ob02.noc.sony.co.jp [211.125.140.165]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3751C2D5922; Tue, 12 May 2026 02:22:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=211.125.140.165 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778552535; cv=none; b=SVuOTZmgVsgUEwQiIHguDU20EXfhmaSb1N47X0CTfLIpqoKUmif22c35ehme7tw4zSyrc9nXTpPvrEWago/2lV5O1K+eTM7pyfimj8ieMpi2Qq5k6cl42gxuP4QUxaUnFOXw6zniZIn2tSOKfaj3SUSSB10urfeN+sgQk7mpZ4M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778552535; c=relaxed/simple; bh=GklZYUKJX6KCfliVPjcXd8Jfg1EfG4Yx/dYPm0oFv3I=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JuS2SEH9iDLLPVvuBkvwabBy4WaOBxQrAczujUA0ouyVL7MgStiOcCLTd6643ZA3fXA0WbuBaVrdMcCFzAmEYhawdcffV80q9v9EV9oIMkFZ9yjFalzWuiz1sMaW5GQPhhwDv8cTm5NmotQRmroRUknCrOYHwqHAhELeYLZ1bz8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sony.com; spf=pass smtp.mailfrom=sony.com; dkim=pass (2048-bit key) header.d=sony.com header.i=@sony.com header.b=AvBtndsj; arc=none smtp.client-ip=211.125.140.165 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sony.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sony.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=sony.com header.i=@sony.com header.b="AvBtndsj" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sony.com; s=s1jp; t=1778552534; x=1810088534; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=hPXs4xfe9WaD1xaFn0d8PPw/gVNLx2J4xPkxz7s4xqs=; b=AvBtndsjAm+PUvUuKW8nrsOYmtuyoaeIXv3dXGIFar4Yu/JE11qgZfGx GQHf2+arX9TBC4x1+jSa24toOLhNr36rWB6l26yXWb8Rso2ZtXUSIe1dU xEyc1uKMblh/pEeFBiaKVHDcnAGZenGiVkRORZff1ej3A9kTIdnFka1L6 RFf97bO1f0sPVkkzxwOyWBcnL9SKDZIbnoMohtBtYkKq10U+g/I8HefpI rZm2ENfpNyk/cs9e1ymui/cu78lYw/PSw9UlDyjAK3yjO1fmGNKyeqy3B 5WpKrvPcBVXObiVU0kVqvfS2BqQoQlTebA8g0sBI65YBz8npAsi3NtpNJ w==; X-CSE-ConnectionGUID: kZC+Y2dPQDWo7xh8pyAsew== X-CSE-MsgGUID: EIn/X9iGRR2/cnYone0EVA== 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; 12 May 2026 11:12:02 +0900 X-CSE-ConnectionGUID: E4sXDblmSuKgQZmCqCcvnA== X-CSE-MsgGUID: Qwx43BEcSKO83PNWSCJ4AQ== X-IronPort-AV: E=Sophos;i="6.23,230,1770562800"; d="scan'208";a="606139396" Received: from unknown (HELO JPC00244420) ([IPv6:2001:cf8:1:573:0:dddd:6b3e:119e]) by jpmta-ob02.noc.sony.co.jp with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 May 2026 11:12:01 +0900 Date: Tue, 12 May 2026 11:12:00 +0900 From: Shashank Balaji To: Thierry Reding , Jonathan Hunter Cc: Gary Guo , 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Hi Thierry, Jonathan, Just following up on the below, would moving tegra194_cbb_driver and tegra234_cbb_driver from pure_initcall to core_initcall work for you? Thanks, Shashank On Tue, Apr 28, 2026 at 10:07:41PM +0900, Shashank Balaji wrote: > 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 >