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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 C0718C47404 for ; Fri, 4 Oct 2019 13:38:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8FE4C20700 for ; Fri, 4 Oct 2019 13:38:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570196297; bh=604gsQxWdPw4qkopFM7tPeLqPTTlm62HSbXH+bbvhO0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=KtaNy8b66wewoDITgUZ4CLuH9fw3vUtfTABTLMdQhRQUGg4wg7o5C8rGhbSLLJtyF aacR0FvxF4ePtI6zIL3/iqRgFeWuW2ZlnK4erO5Ysv7TldaVPDUY8PNIkcVYG9U8mY BRhN1YWayQHtM7QbvGmXXD2kBnw6Xt4cLb8R0udE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388475AbfJDNiQ (ORCPT ); Fri, 4 Oct 2019 09:38:16 -0400 Received: from mx2.suse.de ([195.135.220.15]:38304 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388197AbfJDNiQ (ORCPT ); Fri, 4 Oct 2019 09:38:16 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id E84ACAEF6; Fri, 4 Oct 2019 13:38:14 +0000 (UTC) Date: Fri, 4 Oct 2019 15:38:14 +0200 From: Michal Hocko To: Qian Cai Cc: Anshuman Khandual , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Oscar Salvador , Mel Gorman , Mike Rapoport , Dan Williams , Pavel Tatashin , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/page_alloc: Add a reason for reserved pages in has_unmovable_pages() Message-ID: <20191004133814.GM9578@dhcp22.suse.cz> References: <1570090257-25001-1-git-send-email-anshuman.khandual@arm.com> <20191004105824.GD9578@dhcp22.suse.cz> <91128b73-9a47-100b-d3de-e83f0b941e9f@arm.com> <1570193776.5576.270.camel@lca.pw> <20191004130713.GK9578@dhcp22.suse.cz> <1570195839.5576.273.camel@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1570195839.5576.273.camel@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 04-10-19 09:30:39, Qian Cai wrote: > On Fri, 2019-10-04 at 15:07 +0200, Michal Hocko wrote: > > On Fri 04-10-19 08:56:16, Qian Cai wrote: > > [...] > > > It might be a good time to rethink if it is really a good idea to dump_page() > > > at all inside has_unmovable_pages(). As it is right now, it is a a potential > > > deadlock between console vs memory offline. More details are in this thread, > > > > > > https://lore.kernel.org/lkml/1568817579.5576.172.camel@lca.pw/ > > > > Huh. That would imply we cannot do any printk from that path, no? > > Yes, or use something like printk_deferred() This is just insane. The hotplug code is in no way special wrt printk. It is never called from the printk code AFAIK and thus there is no real reason why this particular code should be any special. Not to mention it calls printk indirectly from a code that is shared with other code paths. > or it needs to rework of the current console locking which I have no > clue yet. Yes, if the lockdep is really referring to a real deadlock which I haven't really explored. -- Michal Hocko SUSE Labs