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=-5.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 2CDC6C43381 for ; Sat, 16 Feb 2019 07:46:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ECAED222D0 for ; Sat, 16 Feb 2019 07:46:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="TkNvWLvz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728972AbfBPHqW (ORCPT ); Sat, 16 Feb 2019 02:46:22 -0500 Received: from mail-pl1-f193.google.com ([209.85.214.193]:42044 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728698AbfBPHqW (ORCPT ); Sat, 16 Feb 2019 02:46:22 -0500 Received: by mail-pl1-f193.google.com with SMTP id s1so6111034plp.9 for ; Fri, 15 Feb 2019 23:46:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=PZ2lrnyrL5JE4u94qbUvHYiQRcN+mxeRBdIawqfw9lE=; b=TkNvWLvzi6rXdW4bbmsjyAQ+azvTiLx5vCvVDnjo4XIW4S6jJk2/WBxmpIA9X8vlYr q+O689VTw0rv/SWPsWJW++8x8uEjhgNZwPrSf5lHMYcjpbT9G6ePLLjMgX4BJXU9KL/t Bk7lv37BarXacmvhQ2gx6LIB3NzLJl69MgDAdfeqWAz3uOE7jLe64FpYi9eH2/vKntwq ZBDoxwHbFksTU/Yi7bgpdorivU30M60DkbRwYWGde+eDjLyGNwaJfVx2DtzBc2lqRh3R BjcfAy2z/mbzKaZcfSwTf944JzstOt9l4BsAoj//7UQfYXWQfRCnQv267kq8Ibo59u7f gdAA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=PZ2lrnyrL5JE4u94qbUvHYiQRcN+mxeRBdIawqfw9lE=; b=D5/K2D9kPLsI2igxvlCrFtbI7c0f7MafxSuKZcB2z328fa8LT/q4hxCltW/q78KpLM DXhkCOduMQHwgkNTbKUM1czkKLxyZotIV8h8dxvjk1vOlwSUpdss4tCPIRztA6nMxttA 0Er2tDfMaycriCz83BPXvAi06DaCkiP57pC2NT95lMUgluFt9O5bjgz0zJIY7SUJ4sTw wodUFMeZ+4N/y5G45ygZRitW3fnXZ3mR9G6CuB4p7RmxYxbaIH2eM0rg2qV1MouBvcC6 WxR/+TnCUKGl7Sh+T8+NeYdJYo/p9taWNkEk4K5DvdK4b2MKtUf3x/p+ghiq2nza29pV 3/vw== X-Gm-Message-State: AHQUAubaGieQd43vFBda0a93gzkWYnd0iJM3T0p90d9Faka0qXjWaBCm SdOpVf/AsLU1qQVcpJvXxBA= X-Google-Smtp-Source: AHgI3Ia6MNcIhv+wZtPN5/q/fU0FawtRAEvEz0qV0YlUODGlryHmTBvzT7e/4Cr1EOv8+L+4zdIiXw== X-Received: by 2002:a17:902:b609:: with SMTP id b9mr14358032pls.57.1550303181083; Fri, 15 Feb 2019 23:46:21 -0800 (PST) Received: from localhost ([221.162.103.114]) by smtp.gmail.com with ESMTPSA id z67sm13153985pfd.188.2019.02.15.23.46.19 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 15 Feb 2019 23:46:20 -0800 (PST) From: Sergey Senozhatsky X-Google-Original-From: Sergey Senozhatsky Date: Sat, 16 Feb 2019 16:46:17 +0900 To: Sergey Senozhatsky Cc: Yao HongBo , linuxarm@huawei.com, linux-kernel@vger.kernel.org Subject: Re: possible deadlock in console_unlock Message-ID: <20190216073856.GA9979@tigerII.localdomain> References: <20190216072127.GA1945@tigerII.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190216072127.GA1945@tigerII.localdomain> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (02/16/19 16:21), Sergey Senozhatsky wrote: > On (02/16/19 14:36), Yao HongBo wrote: > > hi, sergey: > > > > As shown in that link, https://lkml.org/lkml/2018/6/6/397 > > > > On the linux kernel 5.0-rc6, Syzkaller also hit 'possible deadlock in console_unlock' > > bug for several times in my environment. > > > > This solution fixes things for me. Do you have a plan to submit patches to > > solve this problem. > > > > diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c > > __printk_safe_enter(); > > kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); > > __printk_safe_exit(); > > I would probably try the following: Yao HongBo, could you please post the lockdep splat? GFP_NOWARN is probably the best option for now. Yes, it, maybe, will not work for fault-injection cases; but printk_safe approach is harder to push for, especially given that printk_safe maybe will not even exist in the future. -ss