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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 39D61C00140 for ; Wed, 24 Aug 2022 07:14:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235264AbiHXHOC (ORCPT ); Wed, 24 Aug 2022 03:14:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44046 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235300AbiHXHN4 (ORCPT ); Wed, 24 Aug 2022 03:13:56 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B25949412D for ; Wed, 24 Aug 2022 00:13:54 -0700 (PDT) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4MCHMT6TTxznTbG; Wed, 24 Aug 2022 15:11:33 +0800 (CST) Received: from dggpemm500001.china.huawei.com (7.185.36.107) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 24 Aug 2022 15:13:52 +0800 Received: from localhost.localdomain.localdomain (10.175.113.25) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 24 Aug 2022 15:13:52 +0800 From: Kefeng Wang To: Andrew Morton , CC: , , Kefeng Wang Subject: [PATCH 2/2] mm: slince possible data races about pgdat->kswapd Date: Wed, 24 Aug 2022 15:19:09 +0800 Message-ID: <20220824071909.192535-2-wangkefeng.wang@huawei.com> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20220824071909.192535-1-wangkefeng.wang@huawei.com> References: <20220824071909.192535-1-wangkefeng.wang@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.113.25] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The pgdat->kswapd could be accessed concurrently by kswapd_run() and kcompactd(), it don't be protected by any lock, which could leads to data races, adding READ/WRITE_ONCE() to slince it. Signed-off-by: Kefeng Wang --- mm/compaction.c | 4 +++- mm/vmscan.c | 8 ++++---- 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 640fa76228dd..aa1cfe47f046 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1983,7 +1983,9 @@ static inline bool is_via_compact_memory(int order) static bool kswapd_is_running(pg_data_t *pgdat) { - return pgdat->kswapd && task_is_running(pgdat->kswapd); + struct task_struct *t = READ_ONCE(pgdat->kswapd); + + return t && task_is_running(t); } /* diff --git a/mm/vmscan.c b/mm/vmscan.c index 08c6497f76c3..65b19ca8c8ee 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4644,7 +4644,7 @@ void kswapd_run(int nid) pg_data_t *pgdat = NODE_DATA(nid); struct task_struct *t; - if (pgdat->kswapd) + if (READ_ONCE(pgdat->kswapd)) return; t = kthread_run(kswapd, pgdat, "kswapd%d", nid); @@ -4653,7 +4653,7 @@ void kswapd_run(int nid) BUG_ON(system_state < SYSTEM_RUNNING); pr_err("Failed to start kswapd on node %d\n", nid); } else { - pgdat->kswapd = t; + WRITE_ONCE(pgdat->kswapd, t); } } @@ -4663,11 +4663,11 @@ void kswapd_run(int nid) */ void kswapd_stop(int nid) { - struct task_struct *kswapd = NODE_DATA(nid)->kswapd; + struct task_struct *kswapd = READ_ONCE(NODE_DATA(nid)->kswapd); if (kswapd) { kthread_stop(kswapd); - NODE_DATA(nid)->kswapd = NULL; + WRITE_ONCE(NODE_DATA(nid)->kswapd, NULL); } } -- 2.35.3