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Cc: Guopeng Zhang , Ridong Chen , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Chen Ridong , Ridong Chen Subject: [RFC PATCH -v4 04/22] cpuset: introduce partition_enable() Date: Sun, 1 Nov 2026 19:41:48 +0800 Message-Id: <20261101114206.2434398-5-ridong.chen@linux.dev> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20261101114206.2434398-1-ridong.chen@linux.dev> References: <20261101114206.2434398-1-ridong.chen@linux.dev> X-Mailing-List: cgroups@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 From: Chen Ridong Add partition_enable() to consolidate updates to key cpuset structures during partition enablement, including: 1. remote_partition 2. effective_xcpus 3. partition_root_state 4. prs_err Key operations performed: 1. Invokes partition_xcpus_add() to assign exclusive CPUs 2. Maintains remote partition flag 3. Syncs the effective_xcpus mask 4. Updates partition_root_state and prs_err 5. Triggers scheduler domain rebuilds 6. Sends partition change notifications This helper also handles the transition between root and isolated states of a valid partition. In that case the cpumasks are unchanged and only isolated_cpus is updated. A partition_state_update() helper is added to set partition_root_state and prs_err, and to reset the partition data when the new state is not a valid partition. Signed-off-by: Chen Ridong Signed-off-by: Ridong Chen --- kernel/cgroup/cpuset.c | 51 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index df52f6e5e99f..052a131731dd 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1716,6 +1716,57 @@ static void compute_effective_nodemask(nodemask_t *new_mems, nodes_copy(*new_mems, parent->effective_mems); } +static void partition_state_update(struct cpuset *cs, int new_prs, + enum prs_errcode prs_err) +{ + lockdep_assert_held(&callback_lock); + + cs->partition_root_state = new_prs; + WRITE_ONCE(cs->prs_err, prs_err); + if (!is_partition_valid(cs)) + reset_partition_data(cs); +} + +/** + * partition_enable - Transitions a cpuset to a partition root + * @cs: The cpuset to enable partition for + * @parent: Parent cpuset of @cs, NULL for remote parent + * @new_prs: New partition state to set + * @new_excpus: New effective exclusive CPUs mask for the partition + * + * Transitions a cpuset to a partition root, only for v2. + * It also supports the transition between root and isolated partition. + */ +static void partition_enable(struct cpuset *cs, struct cpuset *parent, + int new_prs, struct cpumask *new_excpus) +{ + int old_prs = cs->partition_root_state; + + lockdep_assert_cpuset_lock_held(); + WARN_ON_ONCE(new_prs <= 0); + WARN_ON_ONCE(!cpuset_v2()); + + if (old_prs == new_prs) + return; + + spin_lock_irq(&callback_lock); + if (old_prs > 0) { + /* Switch between root and isolated, cpumasks are unchanged */ + isolated_cpus_update(old_prs, new_prs, cs->effective_xcpus); + } else { + /* enable partition should only add exclusive cpus */ + partition_xcpus_add(new_prs, parent, new_excpus); + /* enable remote partition */ + if (!parent) + cs->remote_partition = true; + cpumask_copy(cs->effective_xcpus, new_excpus); + } + partition_state_update(cs, new_prs, PERR_NONE); + spin_unlock_irq(&callback_lock); + cpuset_force_rebuild(); + notify_partition_change(cs, old_prs); +} + /* * remote_partition_enable - Enable current cpuset as a remote partition root * @cs: the cpuset to update -- 2.34.1