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 5C232C433EF for ; Fri, 22 Apr 2022 23:58:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229680AbiDWABZ (ORCPT ); Fri, 22 Apr 2022 20:01:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57606 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229662AbiDWABY (ORCPT ); Fri, 22 Apr 2022 20:01:24 -0400 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D7FC71E3DFB; Fri, 22 Apr 2022 16:58:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650671909; x=1682207909; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=e3FLOi/+v6B4A3waN/i8lUdjtDM+G0jjnajfyZctWxo=; b=SDp6R0Jq6rA76nJhR1qd9Krc7/kuPoIlPu8AjtGHYzEzBm5dyZlnpVd3 M5EZx+mIZASwD4AOe+UneOSJ8JAOBaST/lsxK9qAApO8Lci8zaLAzsYyX ELSN3rsYBU+I9vYYQoCkfizxbxeh3oFWhCHJIWh631avjW7SecqkC4jbz eIUE5vKHqtfFPnoDd7gIAFDLip8uiRTkDs5Aqt8IQqz2c2RDQ2aLPd9PF Rm1ExLPCq4FNiJck2gLEq0IhfTY1DZo2SJoQMArZePDpF4xRVbG3GlGRJ bSu7NY+tWLKy8Ed29vyuouhuZK9JOy5FJD7hSSWPtONMheDI/tLKS/+Sr A==; X-IronPort-AV: E=McAfee;i="6400,9594,10324"; a="264306798" X-IronPort-AV: E=Sophos;i="5.90,282,1643702400"; d="scan'208";a="264306798" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Apr 2022 16:58:29 -0700 X-IronPort-AV: E=Sophos;i="5.90,282,1643702400"; d="scan'208";a="659264395" Received: from hltravis-mobl1.amr.corp.intel.com (HELO localhost) ([10.213.166.215]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Apr 2022 16:58:28 -0700 Date: Fri, 22 Apr 2022 16:58:28 -0700 From: Ira Weiny To: Dan Williams Cc: linux-cxl@vger.kernel.org, Peter Zijlstra , Greg Kroah-Hartman , "Rafael J. Wysocki" , Ingo Molnar , Will Deacon , Waiman Long , Boqun Feng , Alison Schofield , Vishal Verma , Ben Widawsky , Jonathan Cameron , nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/8] cxl/acpi: Add root device lockdep validation Message-ID: References: <165055518776.3745911.9346998911322224736.stgit@dwillia2-desk3.amr.corp.intel.com> <165055519869.3745911.10162603933337340370.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <165055519869.3745911.10162603933337340370.stgit@dwillia2-desk3.amr.corp.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org On Thu, Apr 21, 2022 at 08:33:18AM -0700, Dan Williams wrote: > The CXL "root" device, ACPI0017, is an attach point for coordinating > platform level CXL resources and is the parent device for a CXL port > topology tree. As such it has distinct locking rules relative to other > CXL subsystem objects, but because it is an ACPI device the lock class > is established well before it is given to the cxl_acpi driver. This final sentence gave me pause because it implied that the device lock class was set to something other than no validate. But I don't see that anywhere in the acpi code. So given that it looks to me like ACPI is just using the default no validate class... Reviewed-by: Ira Weiny > However, the lockdep API does support changing the lock class "live" for > situations like this. Add a device_lock_set_class() helper that a driver > can use in ->probe() to set a custom lock class, and > device_lock_reset_class() to return to the default "no validate" class > before the custom lock class key goes out of scope after ->remove(). > > Note the helpers are all macros to support dead code elimination in the > CONFIG_PROVE_LOCKING=n case. > > Suggested-by: Peter Zijlstra > Cc: Greg Kroah-Hartman > Cc: "Rafael J. Wysocki" > Cc: Ingo Molnar > Cc: Will Deacon > Cc: Waiman Long > Cc: Boqun Feng > Cc: Alison Schofield > Cc: Vishal Verma > Cc: Ira Weiny > Cc: Ben Widawsky > Cc: Jonathan Cameron > Signed-off-by: Dan Williams > --- > drivers/cxl/acpi.c | 15 +++++++++++++++ > include/linux/device.h | 25 +++++++++++++++++++++++++ > 2 files changed, 40 insertions(+) > > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c > index d15a6aec0331..e19cea27387e 100644 > --- a/drivers/cxl/acpi.c > +++ b/drivers/cxl/acpi.c > @@ -275,6 +275,15 @@ static int add_root_nvdimm_bridge(struct device *match, void *data) > return 1; > } > > +static struct lock_class_key cxl_root_key; > + > +static void cxl_acpi_lock_reset_class(void *_dev) > +{ > + struct device *dev = _dev; > + > + device_lock_reset_class(dev); > +} > + > static int cxl_acpi_probe(struct platform_device *pdev) > { > int rc; > @@ -283,6 +292,12 @@ static int cxl_acpi_probe(struct platform_device *pdev) > struct acpi_device *adev = ACPI_COMPANION(host); > struct cxl_cfmws_context ctx; > > + device_lock_set_class(&pdev->dev, &cxl_root_key); > + rc = devm_add_action_or_reset(&pdev->dev, cxl_acpi_lock_reset_class, > + &pdev->dev); > + if (rc) > + return rc; > + > root_port = devm_cxl_add_port(host, host, CXL_RESOURCE_NONE, NULL); > if (IS_ERR(root_port)) > return PTR_ERR(root_port); > diff --git a/include/linux/device.h b/include/linux/device.h > index 93459724dcde..82c9d307e7bd 100644 > --- a/include/linux/device.h > +++ b/include/linux/device.h > @@ -850,6 +850,31 @@ static inline bool device_supports_offline(struct device *dev) > return dev->bus && dev->bus->offline && dev->bus->online; > } > > +#define __device_lock_set_class(dev, name, key) \ > + lock_set_class(&(dev)->mutex.dep_map, name, key, 0, _THIS_IP_) > + > +/** > + * device_lock_set_class - Specify a temporary lock class while a device > + * is attached to a driver > + * @dev: device to modify > + * @key: lock class key data > + * > + * This must be called with the device_lock() already held, for example > + * from driver ->probe(). > + */ > +#define device_lock_set_class(dev, key) \ > + __device_lock_set_class(dev, #key, key) > + > +/** > + * device_lock_reset_class - Return a device to the default lockdep novalidate state > + * @dev: device to modify > + * > + * This must be called with the device_lock() already held, for example > + * from driver ->remove(). > + */ > +#define device_lock_reset_class(dev) \ > + device_lock_set_class(dev, &__lockdep_no_validate__) > + > void lock_device_hotplug(void); > void unlock_device_hotplug(void); > int lock_device_hotplug_sysfs(void); >