From patchwork Mon Oct 18 14:36:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 12566721 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 698FAC433EF for ; Mon, 18 Oct 2021 14:38:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 536216103C for ; Mon, 18 Oct 2021 14:38:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232200AbhJROlG (ORCPT ); Mon, 18 Oct 2021 10:41:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:59040 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231736AbhJROlF (ORCPT ); Mon, 18 Oct 2021 10:41:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1634567933; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=474JE8KDGexTjFdGx4bBirOGDjMm7XbgTSGx/41x5Xw=; b=fd5jgqASSKOm0svok9zioXn6SogEWcqI1gqi3rYwSpCiidsECsuifD/YHGM7+ZPuK39fhM TOEsN5EfzKZCMW9ABp5HXG/cRWaxPab20fcvHNTo/+gLFde+kx1dacUkkmMjP9IC+JmjRz ktCzEBZtvnRJAeP3dVIYM8se9Nfd2Z4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-137-DOmqaj5tPsaZCl6u_vQnag-1; Mon, 18 Oct 2021 10:38:50 -0400 X-MC-Unique: DOmqaj5tPsaZCl6u_vQnag-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9186A80668C; Mon, 18 Oct 2021 14:38:48 +0000 (UTC) Received: from llong.com (unknown [10.22.16.224]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3CD126A8E5; Mon, 18 Oct 2021 14:37:48 +0000 (UTC) From: Waiman Long To: Tejun Heo , Zefan Li , Johannes Weiner , Jonathan Corbet , Shuah Khan Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Morton , Roman Gushchin , Phil Auld , Peter Zijlstra , Juri Lelli , Frederic Weisbecker , Marcelo Tosatti , =?utf-8?q?Michal_Koutn=C3=BD?= , Waiman Long Subject: [PATCH v8 4/6] cgroup/cpuset: Show invalid partition reason string Date: Mon, 18 Oct 2021 10:36:17 -0400 Message-Id: <20211018143619.205065-5-longman@redhat.com> In-Reply-To: <20211018143619.205065-1-longman@redhat.com> References: <20211018143619.205065-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org There are a number of different reasons which can cause a partition to become invalid. A user seeing an invalid partition may not know exactly why. To help user to get a better understanding of the underlying reason, The cpuset.cpus.partition control file, when read, will now report the reason why a partition become invalid. When a partition does become invalid, reading the control file will show "root invalid ()" where is a string that describes why the partition is invalid. Signed-off-by: Waiman Long --- kernel/cgroup/cpuset.c | 48 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 45 insertions(+), 3 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index fab31921728c..9c5ecc8d100c 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -78,6 +78,24 @@ struct fmeter { spinlock_t lock; /* guards read or write of above */ }; +/* + * Invalid partition error code + */ +enum prs_errcode { + PERR_NONE = 0, + PERR_INVCPUS, + PERR_NOCPUS, + PERR_PARENT, + PERR_HOTPLUG, +}; + +static const char * const perr_strings[] = { + [PERR_INVCPUS] = "Invalid change to cpuset.cpus", + [PERR_PARENT] = "Parent is no longer a valid partition root", + [PERR_NOCPUS] = "Parent unable to distribute cpu downstream", + [PERR_HOTPLUG] = "No cpu available due to hotplug", +}; + struct cpuset { struct cgroup_subsys_state css; @@ -163,6 +181,9 @@ struct cpuset { /* Handle for cpuset.cpus.partition */ struct cgroup_file partition_file; + + /* Invalid partition error code, not lock protected */ + enum prs_errcode prs_err; }; /* @@ -275,8 +296,13 @@ static inline int is_partition_root(const struct cpuset *cs) static inline void notify_partition_change(struct cpuset *cs, int old_prs, int new_prs) { - if (old_prs != new_prs) - cgroup_file_notify(&cs->partition_file); + if (old_prs == new_prs) + return; + cgroup_file_notify(&cs->partition_file); + + /* Reset prs_err if not invalid */ + if (new_prs != PRS_ERROR) + WRITE_ONCE(cs->prs_err, PERR_NONE); } static struct cpuset top_cpuset = { @@ -1282,6 +1308,9 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, part_error = partition_is_populated(parent, cpuset) && cpumask_subset(parent->effective_cpus, tmp->addmask) && !cpumask_intersects(tmp->delmask, cpu_active_mask); + + if ((READ_ONCE(cpuset->prs_err) == PERR_NONE) && part_error) + WRITE_ONCE(cpuset->prs_err, PERR_INVCPUS); } else { /* * partcmd_update w/o newmask: @@ -1305,6 +1334,9 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, !parent->nr_subparts_cpus) || (cpumask_equal(parent->effective_cpus, tmp->addmask) && partition_is_populated(parent, cpuset)); + + if (is_partition_root(cpuset) && part_error) + WRITE_ONCE(cpuset->prs_err, PERR_NOCPUS); } if (cmd == partcmd_update) { @@ -1478,6 +1510,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, * When parent is invalid, it has to be too. */ new_prs = PRS_ERROR; + WRITE_ONCE(cp->prs_err, PERR_PARENT); break; } } @@ -2637,6 +2670,7 @@ static s64 cpuset_read_s64(struct cgroup_subsys_state *css, struct cftype *cft) static int sched_partition_show(struct seq_file *seq, void *v) { struct cpuset *cs = css_cs(seq_css(seq)); + const char *err; switch (cs->partition_root_state) { case PRS_ENABLED: @@ -2649,7 +2683,11 @@ static int sched_partition_show(struct seq_file *seq, void *v) seq_puts(seq, "member\n"); break; case PRS_ERROR: - seq_puts(seq, "root invalid\n"); + err = perr_strings[READ_ONCE(cs->prs_err)]; + if (err) + seq_printf(seq, "root invalid (%s)\n", err); + else + seq_puts(seq, "root invalid\n"); break; } return 0; @@ -3256,6 +3294,10 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp) spin_lock_irq(&callback_lock); cs->partition_root_state = PRS_ERROR; spin_unlock_irq(&callback_lock); + if (parent->partition_root_state == PRS_ERROR) + WRITE_ONCE(cs->prs_err, PERR_PARENT); + else + WRITE_ONCE(cs->prs_err, PERR_HOTPLUG); notify_partition_change(cs, old_prs, PRS_ERROR); } cpuset_force_rebuild();