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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 EC099C74A35 for ; Wed, 10 Jul 2019 20:47:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B8D9120844 for ; Wed, 10 Jul 2019 20:47:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="PRy7E8OT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727767AbfGJUrs (ORCPT ); Wed, 10 Jul 2019 16:47:48 -0400 Received: from mail-wr1-f46.google.com ([209.85.221.46]:33754 "EHLO mail-wr1-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726033AbfGJUrr (ORCPT ); Wed, 10 Jul 2019 16:47:47 -0400 Received: by mail-wr1-f46.google.com with SMTP id n9so3910585wru.0 for ; Wed, 10 Jul 2019 13:47:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=5edpXTgbPHCD//rsOftrCCUKU/4KuUV8KkBni52zlLI=; b=PRy7E8OTL4coBxBIK6C3FkWfnnckm2zDhVdPZo/eX6fKIkK8/rfAeuA8aYUGGtZVKU PZtCrzkSZ9rMGs57dppG1NvKIhdnLGQ7s+Qte3YVEIGeOvd8Qebufo/UQHZtOe29ufQr S9CZpZkDSIYutYCrxD69f9hVyVS9KRG0Q7E3fSGvQQeNt1lTQjDrygJ6g/YCjWBWNMMt FSA2O/N2HWtrZw8U0lNRU4odwngIrmVO8nR3a2+GIGTSPaB0tw2TJ+wiNy4zDJemKk9B TVooN4ctdprscAR0Jyg9t45jjZp35vzjpQUOprTwELuiwhZE5qDeE68xG8XaHHNkoUrm o5Bw== 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=5edpXTgbPHCD//rsOftrCCUKU/4KuUV8KkBni52zlLI=; b=EjR1FdtI6NQupCdFkGic64X2FaGDZrpLwGtPhGS/bjHPlijp3h2r97KR89dbbY1kOo mBsDUMNetrQM/aqmG8glVdnlXZHK+wAfvvxlKccoxpoYQ46+rGeWJ3n5kYhBJqqjIYNg UTKHEXxnbtsor4eWc9cL9NAun1jmxqNDOqjgwfviFC8cxYPiPw3c09eYz7RmJtIfnIZe gVrzKnDCGjcC5FQ1TFlZyilgUgVlsIFkVp3Rp55+f8LIzzfjWWzi0cxpfoExm8h4qyck JHgkYrSQJQL/GMaS7e65uzZobs3dAXTo458rtlJ2AzAxxPyIYzycapPNJN0UGrPYzltu Bdhw== X-Gm-Message-State: APjAAAXG0m60SWQY/jabaPMkYwfFT8fnaIF8hNoZUKZWM0siQ7cSoRjM IMsR7W6hL+KdqwKvFlm9hq8= X-Google-Smtp-Source: APXvYqzDJve5qsdNmGOlLU5yLS2CysWNfXfLADq7p/SMBJ4HIg5EWZlSih6U0zv/Y5AMJHkZwO+ipQ== X-Received: by 2002:adf:aacf:: with SMTP id i15mr2030577wrc.124.1562791665965; Wed, 10 Jul 2019 13:47:45 -0700 (PDT) Received: from [192.168.8.147] (31.172.185.81.rev.sfr.net. [81.185.172.31]) by smtp.gmail.com with ESMTPSA id y16sm5584617wrg.85.2019.07.10.13.47.44 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Jul 2019 13:47:45 -0700 (PDT) Subject: Re: BUG: MAX_STACK_TRACE_ENTRIES too low! (2) To: Bart Van Assche , 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: Eric Dumazet Message-ID: Date: Wed, 10 Jul 2019 22:47:43 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/10/19 9:09 PM, Bart Van Assche wrote: > 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. > Can not destroy_workqueue() undo what alloc_workqueue() did ?