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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 0E26FC74A35 for ; Wed, 10 Jul 2019 19:09:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E5A7320651 for ; Wed, 10 Jul 2019 19:09:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728084AbfGJTJh convert rfc822-to-8bit (ORCPT ); Wed, 10 Jul 2019 15:09:37 -0400 Received: from mail-pl1-f172.google.com ([209.85.214.172]:44557 "EHLO mail-pl1-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727612AbfGJTJh (ORCPT ); Wed, 10 Jul 2019 15:09:37 -0400 Received: by mail-pl1-f172.google.com with SMTP id t14so1667936plr.11 for ; Wed, 10 Jul 2019 12:09:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=71riRWOoSktFJs5cdX1C5IGCrBRGHS9gadld7oiJg9A=; b=Q9LsXN7h8e3tUTzee0XzEMarS73bHOrNIQz85hVS8ymqqP5CX2WsIxiDU0xxUHx1c6 5S2OAt/rHig+KS4dmz6dJgHkrVPKDjgQ1AB5qNYb85zwQHFPWLZo/n8WfwLMG38QEwK2 luHzI7rM/jDT4nvSh8Dji5IdtxLYDN8CEWLlA63M/yL/H7LNpj5YU11j46F7aUF3UJ34 1CAwjiEgqMuSy86pELwZgneun4lB4voOm8jCegxOUelZsF3NDYMPGEV9jHkl45wim3hE Ox1S/sP7OhrTqb6Btg8KVgCeNbLdkaq/VfFLvLNfTbZGIN3JutSo17ODPAxCiaOi1WO0 Jduw== X-Gm-Message-State: APjAAAXqjFsFrA7Ar2CVMWghzJvUzvbIRct80vNOMfoWMI0Z7L+M8mdP gt3wjkTOKZNIMVSy05HomR8= X-Google-Smtp-Source: APXvYqzirLrgjYpJGab89dcs2EwsAfBdjjdqR+b6catZXda236vT2M29PT3g8/RRLfSzvPCuK9Qisg== X-Received: by 2002:a17:902:54f:: with SMTP id 73mr39758496plf.246.1562785776376; Wed, 10 Jul 2019 12:09:36 -0700 (PDT) Received: from ?IPv6:2620:15c:2c1:200:fb9c:664d:d2ad:c9b5? ([2620:15c:2c1:200:fb9c:664d:d2ad:c9b5]) by smtp.gmail.com with ESMTPSA id h14sm3044518pfq.22.2019.07.10.12.09.35 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Jul 2019 12:09:35 -0700 (PDT) Subject: Re: BUG: MAX_STACK_TRACE_ENTRIES too low! (2) To: Eric Dumazet , Peter Zijlstra , Ingo Molnar , Will Deacon , linux-kernel@vger.kernel.org, syzbot , syzkaller-bugs@googlegroups.com References: <00000000000089a718058556e1d8@google.com> <20190710053030.GB2152@sol.localdomain> <20190710170057.GB801@sol.localdomain> <20190710172123.GC801@sol.localdomain> <20190710180242.GA193819@gmail.com> <47a9287d-1f02-95d5-a5cf-55f0c0d38378@gmail.com> From: Bart Van Assche Message-ID: Date: Wed, 10 Jul 2019 12:09:34 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <47a9287d-1f02-95d5-a5cf-55f0c0d38378@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/10/19 11:44 AM, Eric Dumazet wrote: > If anything using workqueues in dynamically allocated objects can turn off lockdep, > we have a serious issue. As far as I know that issue is only hit by syzbot tests. Anyway, I see two possible paths forward: * Revert the patch that makes workqueues use dynamic lockdep keys and thereby reintroduce the false positives that lockdep reports if different workqueues share a lockdep key. I think there is agreement that having to analyze lockdep false positives is annoying, time consuming and something nobody likes. * Modify lockdep such that space in its fixed size arrays that is no longer in use gets reused. Since the stack traces saved in the stack_trace[] array have a variable size that array will have to be compacted to avoid fragmentation. Did I overlook anything? Bart.