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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 B8937C43613 for ; Thu, 20 Jun 2019 06:34:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8BC552085A for ; Thu, 20 Jun 2019 06:34:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561012453; bh=Ho986ZwEwN6lSqW02CRO5TRKTGH2igmUfY7a/ULtRRU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=d1a+fmXnulumlmmo8YXLMyo7y33Q4Y2AglRwct1G7uy0c6+Z2+aiBFrHRCR5IVqym Tl8uQSzT4ZxvFCSKhdxQEwZxssq3YH+ezezwYbKPxqKtdLf2Ld2oizFDpfx0+5OarO Wgfh3g+7AXKRonPQrCwpRs/GQbvKJrHCNibD4vGg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726567AbfFTGeM (ORCPT ); Thu, 20 Jun 2019 02:34:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:34302 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725875AbfFTGeL (ORCPT ); Thu, 20 Jun 2019 02:34:11 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 515C62070B; Thu, 20 Jun 2019 06:34:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561012450; bh=Ho986ZwEwN6lSqW02CRO5TRKTGH2igmUfY7a/ULtRRU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lFM3+3jhB60zvG/6yB5IE5B3Rx+VKwvPqzhLzTvAMHSgLqGN5c7UT/x7JJ1TuJGVF lVevF4s7TKlP8/Hj+yX54QMnBdPlf/MMKzNcCIdDbj9TeGMDC6DOu+5ILxmtYZrzRg godWZUUe0caVwlu6le/5vxZ5bW96eLKozu4FLnhk= Date: Thu, 20 Jun 2019 08:34:08 +0200 From: Greg Kroah-Hartman To: Dan Williams Cc: linux-nvdimm , Ingo Molnar , Ira Weiny , Will Deacon , Dave Jiang , Keith Busch , Peter Zijlstra , Vishal Verma , "Rafael J. Wysocki" , Linux Kernel Mailing List Subject: Re: [PATCH 6/6] driver-core, libnvdimm: Let device subsystems add local lockdep coverage Message-ID: <20190620063408.GA4768@kroah.com> References: <156029554317.419799.1324389595953183385.stgit@dwillia2-desk3.amr.corp.intel.com> <156029557585.419799.11741877483838451695.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 19, 2019 at 03:21:58PM -0700, Dan Williams wrote: > On Tue, Jun 11, 2019 at 4:40 PM Dan Williams wrote: > > > > For good reason, the standard device_lock() is marked > > lockdep_set_novalidate_class() because there is simply no sane way to > > describe the myriad ways the device_lock() ordered with other locks. > > However, that leaves subsystems that know their own local device_lock() > > ordering rules to find lock ordering mistakes manually. Instead, > > introduce an optional / additional lockdep-enabled lock that a subsystem > > can acquire in all the same paths that the device_lock() is acquired. > > > > A conversion of the NFIT driver and NVDIMM subsystem to a > > lockdep-validate device_lock() scheme is included. The > > debug_nvdimm_lock() implementation implements the correct lock-class and > > stacking order for the libnvdimm device topology hierarchy. > > Greg, Peter, > > Any thoughts on carrying this debug hack upstream? The idea being that > it's impossible to enable lockdep for the device_lock() globally, but > a constrained usage of the proposed lockdep_mutex has proven enough to > flush out device_lock deadlocks from libnvdimm. > > It appears one aspect that is missing from this patch proposal is a > mechanism / convention to make sure that lockdep_mutex has constrained > usage for a given kernel build, otherwise it's obviously just as > problematic as device_lock(). Other concerns? Yeah, it feels a bit hacky but it's really up to a subsystem to mess up using it as much as anything else, so user beware :) I don't object to it if it makes things easier for you to debug. thanks, greg k-h