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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 9F2D7C43441 for ; Mon, 19 Nov 2018 21:55:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6E6752148E for ; Mon, 19 Nov 2018 21:55:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6E6752148E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=acm.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731887AbeKTIUu (ORCPT ); Tue, 20 Nov 2018 03:20:50 -0500 Received: from mail-pg1-f196.google.com ([209.85.215.196]:47066 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731286AbeKTIUt (ORCPT ); Tue, 20 Nov 2018 03:20:49 -0500 Received: by mail-pg1-f196.google.com with SMTP id w7so14400624pgp.13 for ; Mon, 19 Nov 2018 13:55:09 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=vRH0G4d2svT35SadVTfW/F6JFbG59SEiS8zKIIQR1w8=; b=kbpTm43BotrOKxc8n9/9hEafvI3/1ki/5+VVvQoZzva30vP9M91TQlP+HOaHQx6Ihb 5ovr+mnoiF5Fs18TCcH3vlBBe3fTNcP/QwZh2fSEnxMCBIUiLC65P3JVwoNqyf3jy/ym qk1NIO0JpWHbAR1QVfF+vQSuD3I72ap0cfT/vXFKZW4u45JIxhxxRLipLsrbmB7BUCA0 o9m/TtHCa4QvuJQXm1N95nAxtWsvYJ3zkil9l3iiORAUi3iSTmunJqVgTv80GsKc+vws UljYugmrrEpymAfPLHvPFI/H38uv2vTh0Z7VdJCmhak9rlBdSemMDdTvEOX2Wefc9ufk Hf9A== X-Gm-Message-State: AGRZ1gLiYgtwtIPGExef0ev3W3wMtOvlt2UYyq80d+LCafHHDP/gyen7 mkoyq0ESfgC3jtFeRyujmk4= X-Google-Smtp-Source: AJdET5esgxM9g7fc5YXKiqFlcXU7CqEgbycnH+W43cEmkpRakHAy5UbBPMx9Ur932fxvXB2EW38y9A== X-Received: by 2002:a63:d34a:: with SMTP id u10mr22066759pgi.301.1542664508492; Mon, 19 Nov 2018 13:55:08 -0800 (PST) Received: from ?IPv6:2620:15c:2cd:203:5cdc:422c:7b28:ebb5? ([2620:15c:2cd:203:5cdc:422c:7b28:ebb5]) by smtp.gmail.com with ESMTPSA id l187-v6sm46870861pfc.79.2018.11.19.13.55.07 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 19 Nov 2018 13:55:07 -0800 (PST) Message-ID: <1542664506.185366.64.camel@acm.org> Subject: Re: [PATCH 1/2] locking/lockdep: Add support for dynamic depmaps and keys From: Bart Van Assche To: Peter Zijlstra Cc: mingo@redhat.com, linux-kernel@vger.kernel.org, Will Deacon , Tejun Heo , Johannes Berg Date: Mon, 19 Nov 2018 13:55:06 -0800 In-Reply-To: <20181110135524.GC3339@worktop.programming.kicks-ass.net> References: <20181109234645.10530-1-bvanassche@acm.org> <20181109234645.10530-2-bvanassche@acm.org> <20181110135524.GC3339@worktop.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-7" X-Mailer: Evolution 3.26.2-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2018-11-10 at 14:55 +-0100, Peter Zijlstra wrote: +AD4 On Fri, Nov 09, 2018 at 03:46:44PM -0800, Bart Van Assche wrote: +AD4 +AD4 The lock validator forces to categorize multiple instances of a lock object +AD4 +AD4 as the same lock class because it requires that struct lockdep+AF8-map and struct +AD4 +AD4 lock+AF8-class+AF8-key instances are static objects. This can result in false +AD4 +AD4 positive lockdep reports that are hard to suppress in an elegant way. Hence +AD4 +AD4 add support for allocating instances of these objects dynamically. +AD4 +AD4 Yeah, I think not. You completely fail to explain how what you propose +AD4 is correct. +AD4 +AD4 The thing is+ADs we rely on static objects because they provide +AD4 persistence. Their address will never be re-used. +AD4 +AD4 Dynamic objects do not provide this same guarantee. And when you re-use +AD4 the key address for something else, you'll mix the chains and things +AD4 come unstuck. Hi Peter, Thanks for having taken a look. I will rework this patch taking your feedback into account and will post the new version when it's ready. Bart.