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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11D92C77B7A for ; Thu, 25 May 2023 13:53:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8B11C900003; Thu, 25 May 2023 09:53:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8606B900002; Thu, 25 May 2023 09:53:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 74FE3900003; Thu, 25 May 2023 09:53:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 65B3C900002 for ; Thu, 25 May 2023 09:53:39 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 30CB1160C19 for ; Thu, 25 May 2023 13:53:39 +0000 (UTC) X-FDA: 80828920158.07.F28FDDA Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf15.hostedemail.com (Postfix) with ESMTP id A67D5A000D for ; Thu, 25 May 2023 13:53:35 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=q1PdYS5f; spf=none (imf15.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1685022816; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=AaFFhZ8Vnldn/xVSVKe/XygiXnMD86a4vgEA0lEJGl0=; b=p59ZqZoE3Fw5nwVbYlwFj+lZEAkvYHYUqG0wmy9uTBNTI8Pq2Q04mhT8OA+XfyglHXOa1+ 0LpxsfO2xnoxOFdy/bjMA50i6eFGQbopRCFt3lo2AI9NBMcsCmdp00AsftSxBK0ROmi7ZS saf6bJ5m9J9g0D0ZgyqpTcjp1hh6nf4= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1685022816; a=rsa-sha256; cv=none; b=KMXWEbCA2FHd/94hH7UoBvango3EjZUqE0wR8Rn/oBm+Bv8hKHhFtLZ4AciV/ZvhJU0yO5 MjfowD0HdWvCirfoGmzYDiEClHdXM8uKmafSq8bpli7FYsc4O2AreorHHCrJFvbDm552CD OtTrlLn8PPEVj0M1mzLr95CRLrpcobE= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=q1PdYS5f; spf=none (imf15.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=AaFFhZ8Vnldn/xVSVKe/XygiXnMD86a4vgEA0lEJGl0=; b=q1PdYS5feeji3+jSSRbWcPpzke eRq46d4GQtrx6j8rvXRr06E92WTrn6gZQpmdaDA6LAZvFZyX5obsYeYHaL4ULFDr6RaYHjWZXd2ON leFY7lEMsNFPLG4LlBNrv7cjFTSU0zPnt1JypxKTeGurFpiGxX3MvfYLFdVWekl+MR7j6AE7ntmu3 rxZVcWCuvM7lnB70KnWVR7NUPYj55siLC83Pippg64lHPZ6lxBo8vSSmw+PvOz3DIjKIZ8xXifZSu oK7LxbAWwqwVmR8w91gT+PZ7YichC7z9eQSMAC4rkssKfoaZlbXQ4ZDiPd7OpchK7xgLN1+2a71BM 0zlEkbpg==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1q2BPD-00CEeT-Bz; Thu, 25 May 2023 13:53:27 +0000 Date: Thu, 25 May 2023 14:53:27 +0100 From: Matthew Wilcox To: Karim Manaouil Cc: npiggin@gmail.com, david@redhat.com, akpm@linux-foundation.org, mike.kravetz@oracle.com, linux-mm@kvack.org Subject: Re: mm: Question: pte SMP data race in do_anomyous_page()? Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: ycrgfpogaybhrnq871tw4b9t7zh6g9uz X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: A67D5A000D X-Rspam-User: X-HE-Tag: 1685022815-245099 X-HE-Meta: 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 cnQz6Wg+ ZYDkKLjF98nfgD/Hh9tttMApZP4Id09we59JhNlCB0DF3orl/g5w9xcoL1zzYstHymc2IERxFePoH7tmmPFOmuSurZjVlWZB9pvSXYCIJr3QCvnUd8g6KvBREHAP1OgpsEljAbq4+EXtoNptp5RZoMH0DC/3QmMGD7F2Hj3WyHAX0b+m8g0jmR5tfCbqWihFOCMMtRn7ffuiNX8HzWID4sQjVrmvWqJN5jcUN X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, May 25, 2023 at 11:06:40AM +0100, Karim Manaouil wrote: > Hi, > > In do_anonymous_page(), a new page is allocated and zeroed, and the > corresponding page struct is initialised (setting flags PageUptodate, > PageSwapBacked, etc. and initialising the various counters). > > Then, set_pte_at() is called directly without calling smp_wmb() to make > the updates above visible on other CPUs. How are you able to read the code without reading the comment that explains this? /* * The memory barrier inside __SetPageUptodate makes sure that * preceding stores to the page contents become visible before * the set_pte_at() write. */ __SetPageUptodate(page); entry = mk_pte(page, vma->vm_page_prot); That comment has been there since 2013.