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Mon, 19 Oct 2026 18:10:40 +0000 (UTC) Received: from llong-thinkpadp16vgen1.rmtusnh.csb (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 76B08418; Mon, 19 Oct 2026 18:10:38 +0000 (UTC) From: Waiman Long To: Ridong Chen , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Shuah Khan , Jonathan Corbet , Randy Dunlap Cc: cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Hui Peng , Guopeng Zhang , Waiman Long Subject: [PATCH-next v4 3/9] cgroup/cpuset: Consider all the exclusive CPUs when doing housekeeping check Date: Mon, 19 Oct 2026 14:10:14 -0400 Message-ID: <20261019181020.1069325-4-longman@redhat.com> In-Reply-To: <20261019181020.1069325-1-longman@redhat.com> References: <20261019181020.1069325-1-longman@redhat.com> X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 When prstate_housekeeping_conflict() is called to perform housekeeping check with cpumask changes, the cpumask changes are passed in via add_cpus and del_cpus parameters. With this arrangement, the exclusive CPUs owned by the child partitions and not affected by the cpumask change, if any, are excluded in the analysis. The only places where there are separate add and delete masks are when the cpuset.cpus or cpuset.cpus.exclusive is being changed. In both cases, partition_cpus_change() is a good place to perform the housekeeping check. If we allow a root partition to be created under an isolated partition, it is possible the cpumask change will still leave active housekeeping CPUs but then no housekeeping CPUs will be left when the child partitions are disabled or invalidated. As a first step to protect against this possibility, all the exclusive CPUs of the cpuset should be considered to be owned by the current cpuset when doing housekeeping check. At the same time, we do want to know if some housekeeping CPUs are going to be removed from the isolated partition that there will be no danger of losing all the active housekeeping CPUs. So the current add_cpus paremeter is renamed as new_cpus to indicate that it includes the complete set of effective xcpus. With the new check in partition_cpus_change(), the housekeeping check in update_parent_effective_cpumask() with partcmd_update and newmask is now duplicative and can be removed. The housekeeping check in remote_cpus_update(), however, will still be useful as this function can be called directly from update_cpumasks_hier() without going through partition_cpus_change(). The update_parent_effective_cpumask() call from update_cpumasks_hier() is partcmd_update with no cpumask which still have the housekeeping check and so is covered. Fixes: 103b08709e8a ("cgroup/cpuset: Fail if isolated and nohz_full don't leave any housekeeping") Signed-off-by: Waiman Long --- kernel/cgroup/cpuset.c | 46 +++++++++++++++++++++++++----------------- 1 file changed, 27 insertions(+), 19 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 5acdc3897ef2..cef3cd0a6906 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1356,19 +1356,19 @@ static void partition_xcpus_del(int old_prs, struct cpuset *parent, * prstate_housekeeping_conflict - check for partition & housekeeping conflicts * @new_prs: new partition root state to be checked * @parent_prs: Parent partition root state - * @add_cpus: additional CPUs to be added to current cpuset - * @del_cpus: CPUs to be removed from current cpuset, can be NULL + * @new_cpus: the set of new effective xcpus in the current cpuset + * @del_cpus: old CPUs going to be removed from current cpuset, can be NULL * Return: true if there is conflict, false otherwise * * There are two different housekeeping conflicts to be checked: - * 1) If new_prs is PRS_ROOT, none of the @add_cpus can be a boot-time isolated - * CPU. IOW, the whole @add_cpus must be a subset of HK_TYPE_DOMAIN_BOOT. + * 1) If new_prs is PRS_ROOT, none of the @new_cpus can be a boot-time isolated + * CPU. IOW, the whole @new_cpus must be a subset of HK_TYPE_DOMAIN_BOOT. * 2) If nohz_full is enabled and we have isolated CPUs, their combination must * still leave housekeeping CPUs. This check is only needed if new_prs * differs from parent_prs and one of them is PRS_ISOLATED. */ static bool prstate_housekeeping_conflict(int new_prs, int parent_prs, - struct cpumask *add_cpus, + struct cpumask *new_cpus, struct cpumask *del_cpus) { cpumask_var_t full_hk_cpus; @@ -1393,7 +1393,7 @@ static bool prstate_housekeeping_conflict(int new_prs, int parent_prs, new_prs = -new_prs; if (housekeeping_enabled(HK_TYPE_DOMAIN_BOOT) && (new_prs == PRS_ROOT) && - !cpumask_subset(add_cpus, housekeeping_cpumask(HK_TYPE_DOMAIN_BOOT))) + !cpumask_subset(new_cpus, housekeeping_cpumask(HK_TYPE_DOMAIN_BOOT))) return true; /* @@ -1409,12 +1409,12 @@ static bool prstate_housekeeping_conflict(int new_prs, int parent_prs, return false; /* - * Now make sure that @add_cpus contains new CPUs to be isolated and + * Now make sure that @new_cpus contains new CPUs to be isolated and * @del_cpus contains isolated CPUs to be un-isolated. - * With the guards above, @add_cpus can't be NULL after the swap. + * With the guards above, @new_cpus can't be NULL after the swap. */ if (parent_prs == PRS_ISOLATED) - swap(add_cpus, del_cpus); + swap(new_cpus, del_cpus); if (del_cpus && (cpumask_first_and_and(del_cpus, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE), @@ -1428,7 +1428,7 @@ static bool prstate_housekeeping_conflict(int new_prs, int parent_prs, housekeeping_cpumask(HK_TYPE_DOMAIN)); cpumask_andnot(full_hk_cpus, full_hk_cpus, isolated_cpus); cpumask_and(full_hk_cpus, full_hk_cpus, cpu_active_mask); - res = !cpumask_weight_andnot(full_hk_cpus, add_cpus); + res = !cpumask_weight_andnot(full_hk_cpus, new_cpus); free_cpumask_var(full_hk_cpus); return res; @@ -1718,7 +1718,7 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus, cpumask_subset(top_cpuset.effective_cpus, tmp->addmask)) WRITE_ONCE(cs->prs_err, PERR_NOCPUS); else if (prstate_housekeeping_conflict(prs, PRS_ROOT, - tmp->addmask, tmp->delmask)) + excpus, tmp->delmask)) WRITE_ONCE(cs->prs_err, PERR_HKEEPING); if (cs->prs_err) goto invalidate; @@ -1932,14 +1932,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, parent->effective_xcpus); } - /* - * Check for housekeeping conflicts - */ - if (is_partition_valid(cs) && - prstate_housekeeping_conflict(old_prs, parent_prs, - tmp->delmask, tmp->addmask)) - part_error = PERR_HKEEPING; - /* * The new CPUs to be removed from parent's effective CPUs * must be present. @@ -2470,6 +2462,22 @@ static void partition_cpus_change(struct cpuset *cs, struct cpuset *trialcs, return; prs_err = validate_partition(cs, trialcs); + if (!prs_err && !cpumask_empty(trialcs->effective_xcpus)) { + int prs = cs->partition_root_state; + int parent_prs = is_remote_partition(cs) + ? PRS_ROOT : parent_cs(cs)->partition_root_state; + /* + * Check for housekeeping conflict by passing the whole + * effective_xcpus as well as those CPUs that are to be + * removed from cs as delmask. + */ + cpumask_andnot(tmp->delmask, cs->effective_xcpus, trialcs->effective_xcpus); + if (parent_prs > 0 && + prstate_housekeeping_conflict(prs, parent_prs, + trialcs->effective_xcpus, tmp->delmask)) + prs_err = PERR_HKEEPING; + } + if (prs_err) { WRITE_ONCE(cs->prs_err, prs_err); trialcs->prs_err = prs_err; -- 2.55.0