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 1DE0DC433F5 for ; Mon, 25 Apr 2022 14:43:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8E1066B0074; Mon, 25 Apr 2022 10:43:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 88F3B6B0075; Mon, 25 Apr 2022 10:43:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7573C6B0078; Mon, 25 Apr 2022 10:43:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.27]) by kanga.kvack.org (Postfix) with ESMTP id 660E56B0074 for ; Mon, 25 Apr 2022 10:43:24 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 3765721CF9 for ; Mon, 25 Apr 2022 14:43:24 +0000 (UTC) X-FDA: 79395669528.30.EA57A65 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf18.hostedemail.com (Postfix) with ESMTP id 0BB1A1C0045 for ; Mon, 25 Apr 2022 14:43:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1650897803; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oj3e9OxZuBcl3Mrg5cN9YNi1sy73Km34y8js1iAThkg=; b=hX64EJBF9R1cb2ysYuyf4GlkkH43bB1dClrtfUurIBUyNgn3biwvVpZG9LwtlpWrlRCqRB IqDd1b10qtMy8lwaI/SfvlpxfqXHw7bokaVX6h79OxuhhkZibmHtPr38r4oUsQZw6dofHG hmEtrH0AX11q42Zcoa67/DMCh89xEX4= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-328-hFHyvsjVMym1rU2j_aShaQ-1; Mon, 25 Apr 2022 10:43:19 -0400 X-MC-Unique: hFHyvsjVMym1rU2j_aShaQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id DEB9C29AA3B1; Mon, 25 Apr 2022 14:43:18 +0000 (UTC) Received: from [10.22.9.66] (unknown [10.22.9.66]) by smtp.corp.redhat.com (Postfix) with ESMTP id D6F5214A5067; Mon, 25 Apr 2022 14:43:16 +0000 (UTC) Message-ID: <690fb0ac-6f8c-7e52-2485-4acc030bbc07@redhat.com> Date: Mon, 25 Apr 2022 10:43:16 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH] cgroup/cpuset: Remove redundant cpu/node masks setup in cpuset_init_smp() Content-Language: en-US To: Feng Tang Cc: Tejun Heo , Zefan Li , Johannes Weiner , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Michal Hocko , Dave Hansen , ying.huang@intel.com, stable@vger.kernel.org References: <20220425020926.1264611-1-longman@redhat.com> <20220425073011.GJ46405@shbuild999.sh.intel.com> From: Waiman Long In-Reply-To: <20220425073011.GJ46405@shbuild999.sh.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.85 on 10.11.54.7 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 0BB1A1C0045 X-Stat-Signature: 3cdiqhpkoqki9su983kw6iz6wfz64qdr X-Rspam-User: Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=hX64EJBF; spf=none (imf18.hostedemail.com: domain of longman@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-HE-Tag: 1650897799-31727 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 4/25/22 03:30, Feng Tang wrote: > Hi Waiman, > > Thanks for the patch! > > On Sun, Apr 24, 2022 at 10:09:26PM -0400, Waiman Long wrote: >> There are 3 places where the cpu and node masks of the top cpuset can >> be initialized in the order they are executed: >> 1) start_kernel -> cpuset_init() >> 2) start_kernel -> cgroup_init() -> cpuset_bind() >> 3) kernel_init_freeable() -> do_basic_setup() -> cpuset_init_smp() >> >> The first cpuset_init() function just sets all the bits in the masks. >> The last one executed is cpuset_init_smp() which sets up cpu and node >> masks suitable for v1, but not v2. cpuset_bind() does the right setup >> for both v1 and v2 assuming that effective_mems and effective_cpus have >> been set up properly which is not strictly the case here. As a result, >> cpu and memory node hot add may fail to update the cpu and node masks >> of the top cpuset to include the newly added cpu or node in a cgroup >> v2 environment. >> >> To fix this problem, the redundant cpus_allowed and mems_allowed >> mask setup in cpuset_init_smp() are removed. The effective_cpus and >> effective_mems setup there are moved to cpuset_bind(). >> >> cc: stable@vger.kernel.org >> Signed-off-by: Waiman Long >> --- >> kernel/cgroup/cpuset.c | 10 +++------- >> 1 file changed, 3 insertions(+), 7 deletions(-) >> >> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c >> index 9390bfd9f1cd..a2e15a43397e 100644 >> --- a/kernel/cgroup/cpuset.c >> +++ b/kernel/cgroup/cpuset.c >> @@ -2961,6 +2961,9 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css) >> percpu_down_write(&cpuset_rwsem); >> spin_lock_irq(&callback_lock); >> >> + cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask); >> + top_cpuset.effective_mems = node_states[N_MEMORY]; >> + >> if (is_in_v2_mode()) { >> cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask); >> top_cpuset.mems_allowed = node_possible_map; >> @@ -3390,13 +3393,6 @@ static struct notifier_block cpuset_track_online_nodes_nb = { >> */ >> void __init cpuset_init_smp(void) >> { >> - cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask); >> - top_cpuset.mems_allowed = node_states[N_MEMORY]; >> - top_cpuset.old_mems_allowed = top_cpuset.mems_allowed; >> - >> - cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask); >> - top_cpuset.effective_mems = node_states[N_MEMORY]; > IIUC, the init order is: > cpuset_bind() > smp_init() > cpuset_init_smp() > > while all cpus except boot cpu is brought up in smp_init(), so I'm > thinking moving the cpus_allowed init from cpuset_init_smp() to > cpuset_bind() may cause some problem. Good point. So cpuset_init_smp() is still useful for setting the right effective_cpus and probably effective_mems. I will update the patch accordingly. Thanks, Longman > > Thanks, > Feng >