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=-2.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 F1DAAC65BAE for ; Thu, 13 Dec 2018 09:00:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B57A920672 for ; Thu, 13 Dec 2018 09:00:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="MtBYMcT8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B57A920672 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.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 S1727433AbeLMJAe (ORCPT ); Thu, 13 Dec 2018 04:00:34 -0500 Received: from mail-pl1-f193.google.com ([209.85.214.193]:41225 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725949AbeLMJAd (ORCPT ); Thu, 13 Dec 2018 04:00:33 -0500 Received: by mail-pl1-f193.google.com with SMTP id u6so746229plm.8 for ; Thu, 13 Dec 2018 01:00:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=RbiTCO+OSlfp4GdZoOQfhsM8gZ3dLWt1a+yNSWdYEqc=; b=MtBYMcT8RPsL2Mfzf7AP4bLUpnS7U/cmym3rwjwbHD+JJNU2pWP7ZVtSMvHWBVV+7J ba0FpZRtdPnqDqknB4W0+Dm8DUSOlDXIXf7rSkjtJr4PrJHRKVp5wW2OZqsvEXHPaMVf /PzZdqrbpmdA/ItEo8lOjyr0ggY55sRuO7TF3p32zGeu5qCN58ocVLarAqXUNxoq/5gR ympqaCxVmgPqvlr/IRwhYXoPSlq/uQz9o27jMqQb1wYgYw9el2NoIh9GKu/9vKqPM2HF Q4yedKgbM1IPnxWS3Lqy6XsFOeEJRXmqhE6FOo962X4a1ZA4fjDtoW2Gw12UUimXXQAT U4oQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=RbiTCO+OSlfp4GdZoOQfhsM8gZ3dLWt1a+yNSWdYEqc=; b=MWX3Z54ZauHSVbG3rbSXJeHq6cEJWkSsFzUKEscovhfimngegHQ5+RA4OuLaThsOnz 28bwapExWVrJGodX8oWgqZpbjStkVRQZHuQWzK2FBpsSwIsYqk8fiIXSdN/9LsODPDfN UwrXCFbJi0z0MhVdg8uhg+mn3rJh1EAUmiiml/SBx35sojpwJJ2vXhSN0FClxOvMJQhF xUeX5RDSNeoEhT2oRYYWqTzBSaWrFgtjEsTPKr6jXUtdef38UO4P25CTwP1cQKCUfFHJ ZVQ9awfjFo9m6+bnAIrVfGcuD0XEwHJOHr6XJzZU9kMT1q0aFdfo0s1befladA3oQuQN xr/Q== X-Gm-Message-State: AA+aEWYGX6kTLNkSloqjmYrICuoSZTGGJPm+1moPK3whimKVAAjmoi4C kzo6m8IXLyhOjLzyTnQzmQA= X-Google-Smtp-Source: AFSGD/Wfb6hu3MHQw+bAUqQqDLR6VCn0n99btKRU4n+gWQmZjYVhdcCGOcIn6dxkJjqEpQCAOgswiA== X-Received: by 2002:a17:902:aa0a:: with SMTP id be10mr22489681plb.266.1544691632153; Thu, 13 Dec 2018 01:00:32 -0800 (PST) Received: from localhost ([110.70.59.213]) by smtp.gmail.com with ESMTPSA id z62sm2391122pfl.33.2018.12.13.01.00.30 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 13 Dec 2018 01:00:30 -0800 (PST) Date: Thu, 13 Dec 2018 18:00:27 +0900 From: Sergey Senozhatsky To: Dmitry Safonov <0x7f454c46@gmail.com> Cc: sergey.senozhatsky.work@gmail.com, Dmitry Safonov , longman@redhat.com, Thomas Gleixner , Andrew Morton , open list , Ingo Molnar , Peter Zijlstra , yang.shi@linux.alibaba.com, Arnd Bergmann Subject: Re: [PATCH] debugobjects: Move printk out of db lock critical sections Message-ID: <20181213090026.GA7278@jagdpanzerIV> References: <1544653694-27873-1-git-send-email-longman@redhat.com> <9cb1526a-e82f-dfa7-4b3c-5ea911a8d476@arista.com> <20181213051853.GG4860@jagdpanzerIV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1 (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (12/13/18 05:54), Dmitry Safonov wrote: > > I thought about it for a second, but couldn't figure out if this race > > was real. > > > > E.g. uart case - if there are two paths which concurrently free and > > access debug object, then the same race condition should exist for > > the xmit.buf page. debug object's lifespan should be the same as the > > lifespan of, ummm, whatever the thing that debug object is attached > > to? I'm surely missing something here. > > I think the point of debugobjects is to reduce the damage caused > by an improper life-time of objects. > > IIUC: > 1. alloc_page() > 2. dynamically allocate a workqueue on a new page > 3. schedule some work > 4. until the work has run free_page() Hmm, if we free() that page then __debug_check_no_obj_freed() should ->fixup all ODEBUG_STATE_ACTIVE objects first. Maybe we are talking about different scenarios. -ss