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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 F1790C33CA9 for ; Mon, 13 Jan 2020 16:35:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C2EAA207FD for ; Mon, 13 Jan 2020 16:35:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="XlRk9bRC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729022AbgAMQfA (ORCPT ); Mon, 13 Jan 2020 11:35:00 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:33280 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726943AbgAMQe7 (ORCPT ); Mon, 13 Jan 2020 11:34:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=OyWI+2CxCOjVFobV/HzUixcC6m6SP/UUicEvP6oEb8U=; b=XlRk9bRCU394R+rkkl6rrGt/r6 Qqn9DBhqjxKtJUEgSFbDy5JQNJbJrSLegPLKMIFaGZJU18NogpLUuIVMtSW9KicfpHxIQHnBO/ocW i6b7r6Sypq7BF6c/ab4JiZ9/G5L1ZIk9k7+CCRNARPqSaAzbPWx9fppVhgFp9uixD9X1Ccq6Wkp3i qaaCOJ0wKe++RohEAsXFx/2Fd4hbRAGlSezRtNA9jQ80y1+7E21HirlBOjtVUEsSogU7s6DPjzYcu hkcFwwu2lw67HcSA5E7Nk/AqE+ag7qc1Laiq0dLRZsn/4YzeVcznnqauAkfvMcLgbfs3C3d5NsjI/ kYfSRGdQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1ir2g4-0005KO-K2; Mon, 13 Jan 2020 16:34:56 +0000 Date: Mon, 13 Jan 2020 08:34:56 -0800 From: Matthew Wilcox To: Alex Shi Cc: Konstantin Khlebnikov , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, mgorman@techsingularity.net, tj@kernel.org, hughd@google.com, daniel.m.jordan@oracle.com, yang.shi@linux.alibaba.com, shakeelb@google.com, hannes@cmpxchg.org, Michal Hocko , Vladimir Davydov Subject: Re: [PATCH v7 02/10] mm/memcg: fold lru_lock in lock_page_lru Message-ID: <20200113163456.GA332@bombadil.infradead.org> References: <1577264666-246071-1-git-send-email-alex.shi@linux.alibaba.com> <1577264666-246071-3-git-send-email-alex.shi@linux.alibaba.com> <36d7e390-a3d1-908c-d181-4a9e9c8d3d98@yandex-team.ru> <952d02c2-8aa5-40bb-88bb-c43dee65c8bc@linux.alibaba.com> <2ba8a04e-d8e0-1d50-addc-dbe1b4d8e0f1@yandex-team.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 13, 2020 at 08:47:25PM +0800, Alex Shi wrote: > 在 2020/1/13 下午5:55, Konstantin Khlebnikov 写道: > >>> That's wrong. Here PageLRU must be checked again under lru_lock. > >> Hi, Konstantin, > >> > >> For logical remain, we can get the lock and then release for !PageLRU. > >> but I still can figure out the problem scenario. Would like to give more hints? > > > > That's trivial race: page could be isolated from lru between > > > > if (PageLRU(page)) > > and > > spin_lock_irq(&pgdat->lru_lock); > > yes, it could be a problem. guess the following change could helpful: > I will update it in new version. > + if (lrucare) { > + lruvec = lock_page_lruvec_irq(page); > + if (likely(PageLRU(page))) { > + ClearPageLRU(page); > + del_page_from_lru_list(page, lruvec, page_lru(page)); > + } else { > + unlock_page_lruvec_irq(lruvec); > + lruvec = NULL; > + } What about a harder race to hit like a page being on LRU list A when you look up the lruvec, then it's removed and added to LRU list B by the time you get the lock? At that point, you are holding a lock on the wrong LRU list. I think you need to check not just that the page is still PageLRU but also still on the same LRU list.