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 0B050C43441 for ; Sat, 10 Nov 2018 23:36:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B6AAC20989 for ; Sat, 10 Nov 2018 23:36:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B6AAC20989 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1726839AbeKKJWm (ORCPT ); Sun, 11 Nov 2018 04:22:42 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46270 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725896AbeKKJWm (ORCPT ); Sun, 11 Nov 2018 04:22:42 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id CF33A83F3C; Sat, 10 Nov 2018 23:35:59 +0000 (UTC) Received: from llong.remote.csb (ovpn-120-141.rdu2.redhat.com [10.10.120.141]) by smtp.corp.redhat.com (Postfix) with ESMTP id CC3E3600C5; Sat, 10 Nov 2018 23:35:57 +0000 (UTC) Subject: Re: [RFC PATCH 00/12] locking/lockdep: Add a new class of terminal locks To: Peter Zijlstra , Ingo Molnar Cc: Josh Poimboeuf , Ingo Molnar , Will Deacon , Thomas Gleixner , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, Petr Mladek , Sergey Senozhatsky , Andrey Ryabinin , Tejun Heo , Andrew Morton , Linus Torvalds References: <1541709268-3766-1-git-send-email-longman@redhat.com> <20181109080412.GC86700@gmail.com> <20181110141045.GD3339@worktop.programming.kicks-ass.net> From: Waiman Long Openpgp: preference=signencrypt Autocrypt: addr=longman@redhat.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181110141045.GD3339@worktop.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Sat, 10 Nov 2018 23:36:00 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/10/2018 09:10 AM, Peter Zijlstra wrote: > On Fri, Nov 09, 2018 at 09:04:12AM +0100, Ingo Molnar wrote: >> BTW., if you are interested in more radical approaches to optimize >> lockdep, we could also add a static checker via objtool driven call graph >> analysis, and mark those locks terminal that we can prove are terminal. >> >> This would require the unified call graph of the kernel image and of all >> modules to be examined in a final pass, but that's within the principal >> scope of objtool. (This 'final pass' could also be done during bootup, at >> least in initial versions.) > Something like this is needed for objtool LTO support as well. I just > dread the build time 'regressions' this will introduce :/ > > The final link pass is already by far the most expensive part (as > measured in wall-time) of building a kernel, adding more work there > would really suck :/ I think the idea is to make objtool have the capability to do that. It doesn't mean we need to turn it on by default in every build. Cheers, Longman