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 X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNWANTED_LANGUAGE_BODY,URIBL_BLOCKED,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 2FA02C10F14 for ; Tue, 15 Oct 2019 15:47:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0550420872 for ; Tue, 15 Oct 2019 15:47:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732879AbfJOPrD (ORCPT ); Tue, 15 Oct 2019 11:47:03 -0400 Received: from foss.arm.com ([217.140.110.172]:41402 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732725AbfJOPrD (ORCPT ); Tue, 15 Oct 2019 11:47:03 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 770BB1000; Tue, 15 Oct 2019 08:47:02 -0700 (PDT) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.194.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id C6DA13F68E; Tue, 15 Oct 2019 08:47:00 -0700 (PDT) From: Valentin Schneider To: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Cc: lizefan@huawei.com, tj@kernel.org, hannes@cmpxchg.org, mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, Dietmar.Eggemann@arm.com, morten.rasmussen@arm.com, qperret@google.com, stable@vger.kernel.org Subject: [PATCH v3 1/2] sched/topology: Don't try to build empty sched domains Date: Tue, 15 Oct 2019 16:42:49 +0100 Message-Id: <20191015154250.12951-2-valentin.schneider@arm.com> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20191015154250.12951-1-valentin.schneider@arm.com> References: <20191015154250.12951-1-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Turns out hotplugging CPUs that are in exclusive cpusets can lead to the cpuset code feeding empty cpumasks to the sched domain rebuild machinery. This leads to the following splat: [ 30.618174] Internal error: Oops: 96000004 [#1] PREEMPT SMP [ 30.623697] Modules linked in: [ 30.626731] CPU: 0 PID: 235 Comm: kworker/5:2 Not tainted 5.4.0-rc1-00005-g8d495477d62e #23 [ 30.635003] Hardware name: ARM Juno development board (r0) (DT) [ 30.640877] Workqueue: events cpuset_hotplug_workfn [ 30.645713] pstate: 60000005 (nZCv daif -PAN -UAO) [ 30.650464] pc : build_sched_domains (./include/linux/arch_topology.h:23 kernel/sched/topology.c:1898 kernel/sched/topology.c:1969) [ 30.655126] lr : build_sched_domains (kernel/sched/topology.c:1966) [...] [ 30.742047] Call trace: [ 30.744474] build_sched_domains (./include/linux/arch_topology.h:23 kernel/sched/topology.c:1898 kernel/sched/topology.c:1969) [ 30.748793] partition_sched_domains_locked (kernel/sched/topology.c:2250) [ 30.753971] rebuild_sched_domains_locked (./include/linux/bitmap.h:370 ./include/linux/cpumask.h:538 kernel/cgroup/cpuset.c:955 kernel/cgroup/cpuset.c:978 kernel/cgroup/cpuset.c:1019) [ 30.758977] rebuild_sched_domains (kernel/cgroup/cpuset.c:1032) [ 30.763209] cpuset_hotplug_workfn (kernel/cgroup/cpuset.c:3205 (discriminator 2)) [ 30.767613] process_one_work (./arch/arm64/include/asm/jump_label.h:21 ./include/linux/jump_label.h:200 ./include/trace/events/workqueue.h:114 kernel/workqueue.c:2274) [ 30.771586] worker_thread (./include/linux/compiler.h:199 ./include/linux/list.h:268 kernel/workqueue.c:2416) [ 30.775217] kthread (kernel/kthread.c:255) [ 30.778418] ret_from_fork (arch/arm64/kernel/entry.S:1167) [ 30.781965] Code: f860dae2 912802d6 aa1603e1 12800000 (f8616853) The faulty line in question is cap = arch_scale_cpu_capacity(cpumask_first(cpu_map)); and we're not checking the return value against nr_cpu_ids (we shouldn't have to!), which leads to the above. Prevent generate_sched_domains() from returning empty cpumasks, and add some assertion in build_sched_domains() to scream bloody murder if it happens again. The above splat was obtained on my Juno r0 with: cgcreate -g cpuset:asym cgset -r cpuset.cpus=0-3 asym cgset -r cpuset.mems=0 asym cgset -r cpuset.cpu_exclusive=1 asym cgcreate -g cpuset:smp cgset -r cpuset.cpus=4-5 smp cgset -r cpuset.mems=0 smp cgset -r cpuset.cpu_exclusive=1 smp cgset -r cpuset.sched_load_balance=0 . echo 0 > /sys/devices/system/cpu/cpu4/online echo 0 > /sys/devices/system/cpu/cpu5/online Cc: Fixes: 05484e098448 ("sched/topology: Add SD_ASYM_CPUCAPACITY flag detection") Signed-off-by: Valentin Schneider --- kernel/cgroup/cpuset.c | 8 ++++++++ kernel/sched/topology.c | 5 ++++- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index c52bc91f882b..a859e5539440 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -817,6 +817,11 @@ static int generate_sched_domains(cpumask_var_t **domains, struct cpuset *a = csa[i]; int apn = a->pn; + if (cpumask_empty(a->effective_cpus)) { + ndoms--; + continue; + } + for (j = 0; j < csn; j++) { struct cpuset *b = csa[j]; int bpn = b->pn; @@ -859,6 +864,9 @@ static int generate_sched_domains(cpumask_var_t **domains, continue; } + if (cpumask_empty(a->effective_cpus)) + continue; + dp = doms[nslot]; if (nslot == ndoms) { diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index b5667a273bf6..9318acf1d1fe 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -1948,7 +1948,7 @@ static struct sched_domain_topology_level static int build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *attr) { - enum s_alloc alloc_state; + enum s_alloc alloc_state = sa_none; struct sched_domain *sd; struct s_data d; struct rq *rq = NULL; @@ -1956,6 +1956,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att struct sched_domain_topology_level *tl_asym; bool has_asym = false; + if (WARN_ON(cpumask_empty(cpu_map))) + goto error; + alloc_state = __visit_domain_allocation_hell(&d, cpu_map); if (alloc_state != sa_rootdomain) goto error; -- 2.22.0