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 6AAA9C433F5 for ; Wed, 9 Feb 2022 12:07:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232286AbiBIMHL (ORCPT ); Wed, 9 Feb 2022 07:07:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232678AbiBIMGF (ORCPT ); Wed, 9 Feb 2022 07:06:05 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 01D0DC094C96; Wed, 9 Feb 2022 03:26:34 -0800 (PST) Received: from dggpemm500021.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4JtyGy1t4wzbk7K; Wed, 9 Feb 2022 19:25:30 +0800 (CST) Received: from dggpemm500002.china.huawei.com (7.185.36.229) by dggpemm500021.china.huawei.com (7.185.36.109) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Wed, 9 Feb 2022 19:26:31 +0800 Received: from [10.174.179.5] (10.174.179.5) by dggpemm500002.china.huawei.com (7.185.36.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Wed, 9 Feb 2022 19:26:30 +0800 Subject: Re: [PATCH 0/2] mm/page_alloc: Remote per-cpu lists drain support To: Nicolas Saenz Julienne , CC: , , , , , , , , , , References: <20220208100750.1189808-1-nsaenzju@redhat.com> <7c87f388-cc50-e9a1-17a7-802bb42656e4@huawei.com> From: Xiongfeng Wang Message-ID: Date: Wed, 9 Feb 2022 19:26:29 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.5] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500002.china.huawei.com (7.185.36.229) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 2022/2/9 17:45, Nicolas Saenz Julienne wrote: > Hi Xiongfeng, thanks for taking the time to look at this. > > On Wed, 2022-02-09 at 16:55 +0800, Xiongfeng Wang wrote: >> Hi Nicolas， >> >> When I applied the patchset on the following commit and tested on QEMU, I came >> accross the following CallTrace. >> commit dd81e1c7d5fb126e5fbc5c9e334d7b3ec29a16a0 >> >> I wrote a userspace application to consume the memory. When the memory is used >> out, the OOM killer is triggered and the following Calltrace is printed. I am >> not sure if it is related to this patchset. But when I reverted this patchset, >> the 'NULL pointer' Calltrace didn't show. > > It's a silly mistake on my part, while cleaning up the code I messed up one of > the 'struct per_cpu_pages' accessors. This should fix it: > > ------------------------->8------------------------- > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 0caa7155ca34..e65b991c3dc8 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3279,7 +3279,7 @@ static void __drain_all_pages(struct zone *zone, bool force_all_cpus) > has_pcps = true; > } else { > for_each_populated_zone(z) { > - pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu); > + pcp = per_cpu_ptr(z->per_cpu_pageset, cpu); > lp = rcu_dereference_protected(pcp->lp, > mutex_is_locked(&pcpu_drain_mutex)); > if (lp->count) { I have tested it. It works well. No more 'NULL pointer' Calltrace. Thanks, Xiongfeng > ------------------------->8------------------------- > > Thanks! >