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=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 8EB8EC433EF for ; Wed, 15 Sep 2021 04:10:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2141260FC0 for ; Wed, 15 Sep 2021 04:10:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 2141260FC0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 6EA786B0071; Wed, 15 Sep 2021 00:10:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 699666B0072; Wed, 15 Sep 2021 00:10:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 56179900002; Wed, 15 Sep 2021 00:10:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0004.hostedemail.com [216.40.44.4]) by kanga.kvack.org (Postfix) with ESMTP id 446B16B0071 for ; Wed, 15 Sep 2021 00:10:29 -0400 (EDT) Received: from smtpin33.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id D4E7418294F86 for ; Wed, 15 Sep 2021 04:10:28 +0000 (UTC) X-FDA: 78588480936.33.6F34D97 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf05.hostedemail.com (Postfix) with ESMTP id 98EE65059E91 for ; Wed, 15 Sep 2021 04:10:28 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 9045260E74; Wed, 15 Sep 2021 04:10:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1631679027; bh=ZOLv9LtY30tSZai91s3Z+6sLPL5sOEycDB8UHDM+dXg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Lo/2zCrWRyCnKbpX+cCAP3SyT8q6BnwIG9t4mdApLxg1PWcsSdxLSZF7MlvLLDhV6 dRy2jbObw2LgGJUNaD/V94Wju23pwnMVNQh+NFJ63QRN9jpJKnTbF4AZLLjwq7NhNo jRkJdY6znaIN7Qa+y7NOMm/DzxkX6/dE0AiZTz0A= Date: Tue, 14 Sep 2021 21:10:27 -0700 From: Andrew Morton To: Liu Shixin Cc: "Paul E . McKenney" , , Subject: Re: [PATCH] mm/vmstat: annotate data race for zone->free_area[order].nr_free Message-Id: <20210914211027.0d612d99a94b085112ba0969@linux-foundation.org> In-Reply-To: <20210908015606.3999871-1-liushixin2@huawei.com> References: <20210908015606.3999871-1-liushixin2@huawei.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b="Lo/2zCrW"; spf=pass (imf05.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 98EE65059E91 X-Stat-Signature: ip7ksxdo4mqhpe8f9j14daecpjrubcii X-HE-Tag: 1631679028-326535 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000076, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 8 Sep 2021 09:56:06 +0800 Liu Shixin wrote: > KCSAN reports a data-race on v5.10 which also exists on mainline: > > ================================================================== > BUG: KCSAN: data-race in extfrag_for_order+0x33/0x2d0 > > race at unknown origin, with read to 0xffff9ee9bfffab48 of 8 bytes by task 34 on cpu 1: > extfrag_for_order+0x33/0x2d0 > kcompactd+0x5f0/0xce0 > kthread+0x1f9/0x220 > ret_from_fork+0x22/0x30 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 PID: 34 Comm: kcompactd0 Not tainted 5.10.0+ #2 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 > ================================================================== > > Access to zone->free_area[order].nr_free in extfrag_for_order()/frag_show_print() > is lockless. That's intentional and the stats are a rough estimate anyway. > Annotate them with data_race(). checkpatch helpfully says WARNING: data_race without comment #40: FILE: mm/vmstat.c:1074: + blocks = data_race(zone->free_area[order].nr_free); can we please add a comment ;)