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 1A140C433FE for ; Mon, 25 Apr 2022 07:30:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A31688D000B; Mon, 25 Apr 2022 03:30:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9B8B78D0006; Mon, 25 Apr 2022 03:30:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 85A628D000B; Mon, 25 Apr 2022 03:30:18 -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 726648D0006 for ; Mon, 25 Apr 2022 03:30:18 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 4FFC528830 for ; Mon, 25 Apr 2022 07:30:18 +0000 (UTC) X-FDA: 79394578116.13.F9962C7 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by imf12.hostedemail.com (Postfix) with ESMTP id 273474002E for ; Mon, 25 Apr 2022 07:30:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650871817; x=1682407817; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=v33AZ1EXAwq6WXUADhV0AAEUbQzxeq80/j/EQgk+qSk=; b=iWGovPrFYzlsyqXkxjPQKVCSDs3yUQuaOYkm9Z/ULHrkeZx1qYoNvxqB NtR4/2Zf48jIBkOsPVNRZPveoX3P9BfDmcmpLGFICatRwTByi1kfvyQV8 Eq/KIG73qIcemF5F2+QAbdAF4vwHbSX/re3IYk+kSV41RhLPB67hEYpKj xT5s1LKazcuRIXClstOb+Lhz68w/RGhrjd/SyGRjELoUmfGrSsz4VkZdG sgMSVKHyppgZ1GIxRLPSkPuxWYrFZ4s2PCGF+EGMcywOAxGIzZpR02wZq J4w9MWmxL0dy6hTb6xTOhb2d2EaCMXbWpgy0Yvf4Pgj1fSRBglZQTE2s9 A==; X-IronPort-AV: E=McAfee;i="6400,9594,10327"; a="351616702" X-IronPort-AV: E=Sophos;i="5.90,287,1643702400"; d="scan'208";a="351616702" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2022 00:30:15 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.90,287,1643702400"; d="scan'208";a="531983853" Received: from shbuild999.sh.intel.com (HELO localhost) ([10.239.146.138]) by orsmga006.jf.intel.com with ESMTP; 25 Apr 2022 00:30:12 -0700 Date: Mon, 25 Apr 2022 15:30:11 +0800 From: Feng Tang To: Waiman Long 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 Subject: Re: [PATCH] cgroup/cpuset: Remove redundant cpu/node masks setup in cpuset_init_smp() Message-ID: <20220425073011.GJ46405@shbuild999.sh.intel.com> References: <20220425020926.1264611-1-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220425020926.1264611-1-longman@redhat.com> X-Stat-Signature: kqk93enxh95wucwb13pi4tmpzkuwxxwe X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 273474002E X-Rspam-User: Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=iWGovPrF; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf12.hostedemail.com: domain of feng.tang@intel.com has no SPF policy when checking 192.55.52.43) smtp.mailfrom=feng.tang@intel.com X-HE-Tag: 1650871809-237057 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: 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. Thanks, Feng