From patchwork Sat Sep 18 08:46:55 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Liu Shixin X-Patchwork-Id: 12503685 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 34D28C433EF for ; Sat, 18 Sep 2021 08:18:37 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BFC0C6124B for ; Sat, 18 Sep 2021 08:18:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org BFC0C6124B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 3778A6B0071; Sat, 18 Sep 2021 04:18:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 327736B0072; Sat, 18 Sep 2021 04:18:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 23CD16B0073; Sat, 18 Sep 2021 04:18:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0204.hostedemail.com [216.40.44.204]) by kanga.kvack.org (Postfix) with ESMTP id 145826B0071 for ; Sat, 18 Sep 2021 04:18:36 -0400 (EDT) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id A4B2A2D3AD for ; Sat, 18 Sep 2021 08:18:35 +0000 (UTC) X-FDA: 78599992590.19.7F72C9A Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by imf02.hostedemail.com (Postfix) with ESMTP id BCCC57001A05 for ; Sat, 18 Sep 2021 08:18:34 +0000 (UTC) Received: from dggemv711-chm.china.huawei.com (unknown [172.30.72.54]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4HBNwv0strz8tDw; Sat, 18 Sep 2021 16:17:51 +0800 (CST) Received: from dggpemm500009.china.huawei.com (7.185.36.225) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Sat, 18 Sep 2021 16:18:29 +0800 Received: from huawei.com (10.175.113.32) by dggpemm500009.china.huawei.com (7.185.36.225) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Sat, 18 Sep 2021 16:18:29 +0800 From: Liu Shixin To: Andrew Morton CC: , , Liu Shixin Subject: [PATCH v2] mm/vmstat: annotate data race for zone->free_area[order].nr_free Date: Sat, 18 Sep 2021 16:46:55 +0800 Message-ID: <20210918084655.2696522-1-liushixin2@huawei.com> X-Mailer: git-send-email 2.18.0.huawei.25 MIME-Version: 1.0 X-Originating-IP: [10.175.113.32] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500009.china.huawei.com (7.185.36.225) X-CFilter-Loop: Reflected Authentication-Results: imf02.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=huawei.com; spf=pass (imf02.hostedemail.com: domain of liushixin2@huawei.com designates 45.249.212.189 as permitted sender) smtp.mailfrom=liushixin2@huawei.com X-Stat-Signature: eng5pehxr8tnfwsa65ta8ypziez4tduj X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: BCCC57001A05 X-HE-Tag: 1631953114-295365 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000068, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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() and frag_show_print() is lockless. That's intentional and the stats are a rough estimate anyway. Annotate them with data_race(). Signed-off-by: Liu Shixin --- mm/vmstat.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/mm/vmstat.c b/mm/vmstat.c index 8ce2620344b2..8525849a48f0 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1070,8 +1070,13 @@ static void fill_contig_page_info(struct zone *zone, for (order = 0; order < MAX_ORDER; order++) { unsigned long blocks; - /* Count number of free blocks */ - blocks = zone->free_area[order].nr_free; + /* + * Count number of free blocks. + * + * Access to nr_free is lockless as nr_free is used only for + * diagnostic purposes. Use data_race to avoid KCSAN warning. + */ + blocks = data_race(zone->free_area[order].nr_free); info->free_blocks_total += blocks; /* Count free base pages */ @@ -1445,7 +1450,11 @@ static void frag_show_print(struct seq_file *m, pg_data_t *pgdat, seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name); for (order = 0; order < MAX_ORDER; ++order) - seq_printf(m, "%6lu ", zone->free_area[order].nr_free); + /* + * Access to nr_free is lockless as nr_free is used only for + * printing purposes. Use data_race to avoid KCSAN warning. + */ + seq_printf(m, "%6lu ", data_race(zone->free_area[order].nr_free)); seq_putc(m, '\n'); }