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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 4A16DC43441 for ; Mon, 19 Nov 2018 17:41:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1A9342145D for ; Mon, 19 Nov 2018 17:41:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1A9342145D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz 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 S2389584AbeKTDNL (ORCPT ); Mon, 19 Nov 2018 22:13:11 -0500 Received: from mx2.suse.de ([195.135.220.15]:36468 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2387988AbeKTDNJ (ORCPT ); Mon, 19 Nov 2018 22:13:09 -0500 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 5B3E9AF6C; Mon, 19 Nov 2018 16:48:55 +0000 (UTC) Subject: Re: Memory hotplug softlock issue To: Michal Hocko Cc: Baoquan He , David Hildenbrand , linux-mm@kvack.org, pifang@redhat.com, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, aarcange@redhat.com, Mel Gorman , Hugh Dickins References: <20181115131927.GT23831@dhcp22.suse.cz> <20181115133840.GR2653@MiWiFi-R3L-srv> <20181115143204.GV23831@dhcp22.suse.cz> <20181116012433.GU2653@MiWiFi-R3L-srv> <20181116091409.GD14706@dhcp22.suse.cz> <20181119105202.GE18471@MiWiFi-R3L-srv> <20181119124033.GJ22247@dhcp22.suse.cz> <20181119125121.GK22247@dhcp22.suse.cz> <20181119141016.GO22247@dhcp22.suse.cz> <20181119164618.GQ22247@dhcp22.suse.cz> From: Vlastimil Babka Openpgp: preference=signencrypt Autocrypt: addr=vbabka@suse.cz; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1 MIME-Version: 1.0 In-Reply-To: <20181119164618.GQ22247@dhcp22.suse.cz> 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 11/19/18 5:46 PM, Michal Hocko wrote: > On Mon 19-11-18 17:36:21, Vlastimil Babka wrote: >> >> So what protects us from locking a page whose refcount dropped to zero? >> and is being freed? The checks in freeing path won't be happy about a >> stray lock. > > Nothing really prevents that. But does it matter. The worst that might > happen is that we lock a freed or reused page. Who would complain? free_pages_check() for example PAGE_FLAGS_CHECK_AT_FREE includes PG_locked