Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752950AbbF2PgH (ORCPT ); Mon, 29 Jun 2015 11:36:07 -0400 Received: from mga09.intel.com ([134.134.136.24]:11083 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752428AbbF2PgD (ORCPT ); Mon, 29 Jun 2015 11:36:03 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,699,1427785200"; d="scan'208";a="755214618" Message-ID: <559165E1.105@linux.intel.com> Date: Mon, 29 Jun 2015 08:36:01 -0700 From: Arjan van de Ven User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Mark Brown CC: Nicolas Boichat , Lars-Peter Clausen , Mauro Carvalho Chehab , Antti Palosaari , Ingo Molnar , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Bard Liao , Oder Chiou , Liam Girdwood , Jaroslav Kysela , Takashi Iwai , alsa-devel@alsa-project.org, Anatol Pomozov Subject: Re: [RFC PATCH 1/2] regmap: add configurable lock class key for lockdep References: <558C1824.8020204@metafoo.de> <20150625153325.GR14071@sirena.org.uk> <558C229D.4090409@metafoo.de> <20150625160817.GT14071@sirena.org.uk> <5591414D.6080802@metafoo.de> <20150629142215.GE11162@sirena.org.uk> <559157A8.2050206@linux.intel.com> <20150629153256.GF11162@sirena.org.uk> In-Reply-To: <20150629153256.GF11162@sirena.org.uk> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1823 Lines: 47 On 6/29/2015 8:32 AM, Mark Brown wrote: > On Mon, Jun 29, 2015 at 07:35:20AM -0700, Arjan van de Ven wrote: > >> lockdep assumes that there is a known lock hierarchy, at least known >> to the developer. > >> seems like for regmap there isn't > > It's not that there's no heirachy of locks, it's that lockdep is unable > to understand what's going on since it's making simplifying assumptions > that just aren't true. If I remember the problem correctly it's > grouping all locks allocated in the same place into one class which > doesn't work at all for scenarios where you've got a generic interface > providing services to many devices which may be stacked on top of each > other. but the stacking *IS* a lock hierarchy. it just seems that the hierarchy is implied rather than explicit. >> (I would be interested to know how you avoid ABBA deadlocks btw, >> can you have 2 devices, one with a hierarchy one way, and another >> with the hierarchy the other way?) > > I'm not sure I fully understand what you mean here, sorry - do you mean > in terms of classes or individual devices? The relationships between > devices are all device and system defined, individual regmaps should be > treated as separate classes. From this perspective it's basically > eqivalent to asking how the mutex code avoids misuse of mutexes. well what I meant is inividual devices/ranges like device A is on devmap A but then ends up using devmap B underneath (e.g. the lock nesting case) what prevents there from being a device B that is on devmap B but that uses devmap A underneath > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/