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Mon, 09 Nov 2026 08:37:05 -0800 (PST) Received: from victus-lab ([193.205.81.5]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4b96cd012e1sm138851295e9.8.2026.11.09.08.37.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Nov 2026 08:37:04 -0800 (PST) From: Yuri Andriaccio To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Luca Abeni , Yuri Andriaccio Subject: [RFC PATCH v7 28/29] sched/rt: Prevent CPU offline operation on active rt-cgroups. Date: Mon, 9 Nov 2026 17:36:14 +0100 Message-ID: <20261109163616.195264-29-yurand2000@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261109163616.195264-1-yurand2000@gmail.com> References: <20261109163616.195264-1-yurand2000@gmail.com> X-Mailing-List: linux-kernel@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 Introduce tg_can_offline_cpu and prevent CPU offlining if any rt-cgroup has requested bandwidth on the offlining core. Signed-off-by: Yuri Andriaccio --- kernel/sched/core.c | 3 +++ kernel/sched/rt.c | 27 +++++++++++++++++++++++++++ kernel/sched/sched.h | 1 + 3 files changed, 31 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 59bd9599c509..4321be11c6c7 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8717,6 +8717,9 @@ int sched_cpu_deactivate(unsigned int cpu) struct rq *rq = cpu_rq(cpu); int ret; + if (!tg_can_offline_cpu(cpu)) + return -EBUSY; + ret = dl_bw_deactivate(cpu); if (ret) diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 37e4b24183ab..e5f05aeabd5c 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2853,6 +2853,33 @@ int cpuset_can_change(struct cgroup *cgroup) { return 1; } +static int __tg_can_offline_cpu(struct task_group *tg, void *data) { + const struct dl_bandwidth *dl_b; + int *d = data; + int cpu = *d; + + if (tg == &root_task_group) + return 0; + + guard(raw_spinlock_irq)(dl_bw_lock_of_tg(tg)); + dl_b = dl_bandwidth_read(tg); + if (dl_b->dl_runtime == RUNTIME_INF) + return 0; + + return cpumask_test_cpu(cpu, dl_b->active_mask); +} + +int tg_can_offline_cpu(int cpu) { + if (!rt_group_sched_enabled()) + return 1; + + guard(rcu)(); + if (walk_tg_tree(__tg_can_offline_cpu, tg_nop, &cpu)) + return 0; + + return 1; +} + int sched_rt_can_attach(struct task_group *tg) { struct task_group *ctx; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 9410d1909729..a6aae4375a31 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -590,6 +590,7 @@ extern int tg_rt_internal_bandwidth(struct task_group *tg, int cpu, u64 *rt_period_us, u64 *rt_runtime_us); extern int tg_set_rt_bandwidth(struct task_group *tg, u64 rt_period_us, u64 rt_runtime_us); +extern int tg_can_offline_cpu(int cpu); extern int sched_rt_can_attach(struct task_group *tg); extern struct task_group *sched_create_group(struct task_group *parent); -- 2.56.0