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Mon, 09 Nov 2026 08:36:44 -0800 (PST) Received: from victus-lab ([193.205.81.5]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4b96cd012e1sm138851295e9.8.2026.11.09.08.36.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Nov 2026 08:36:44 -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 14/29] sched/rt: Update task event callbacks for HCBS scheduling Date: Mon, 9 Nov 2026 17:36:00 +0100 Message-ID: <20261109163616.195264-15-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 Update wakeup_preempt_rt, switched_{from/to}_rt and prio_changed_rt with rt-cgroup's specific preemption rules: - In wakeup_preempt_rt(), whenever a task wakes up, it must be checked if it is served by a deadline server or it lives on the global runqueue. Preemption rules (as documented in the function), change based on the current task's donor and woken task runqueue: - If both tasks are FIFO/RR tasks on the global runqueue, or the same cgroup, run as normal. - If woken is inside a cgroup, but donor is a FIFO task on the global runqueue, always preempt. If donor is a DEADLINE task, check if the dl server preempts donor. - If both tasks are FIFO/RR tasks in served but different groups, check whether the woken server preempts the donor server. - In prio_changed_rt(), if the task is not running, only run preemption checks if the running task resides on the same task group of the task that changed priority. Update sched_rt_can_attach() to check if a task can be attached to a given cgroup. For now the check only consists in checking if the group has non-zero bandwidth. Remove the tsk argument from sched_rt_can_attach, as it is unused. Change cpu_cgroup_can_attach() to check if the attachee is a FIFO/RR task before attaching it to a cgroup. Update __sched_setscheduler() to perform checks when trying to switch to FIFO/RR for a task inside a cgroup, as the group needs to have runtime allocated. Update task_is_throttled_rt() for SCHED_CORE, returning the is_throttled value of the server if present, while global rt-tasks are never throttled. Update migration functions to ignore cgroups migration, to be implemented in later patches. Co-developed-by: Alessio Balsini Signed-off-by: Alessio Balsini Co-developed-by: Andrea Parri Signed-off-by: Andrea Parri Co-developed-by: luca abeni Signed-off-by: luca abeni Signed-off-by: Yuri Andriaccio --- kernel/sched/core.c | 2 +- kernel/sched/rt.c | 108 +++++++++++++++++++++++++++++++++++++--- kernel/sched/sched.h | 2 +- kernel/sched/syscalls.c | 12 +++++ 4 files changed, 115 insertions(+), 9 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f1d43e77c711..0425d2c98240 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -9577,7 +9577,7 @@ static int cpu_cgroup_can_attach(struct cgroup_taskset *tset) goto scx_check; cgroup_taskset_for_each(task, css, tset) { - if (!sched_rt_can_attach(css_tg(css), task)) + if (rt_task(task) && !sched_rt_can_attach(css_tg(css))) return -EINVAL; } scx_check: diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index ec0198902b70..b7ea6b5da9e4 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -372,6 +372,9 @@ static inline void rt_queue_push_tasks(struct rt_rq *rt_rq) { struct rq *rq = global_rq_of_rt_rq(rt_rq); + if (is_dl_group(rt_rq)) + return; + if (!has_pushable_tasks(rt_rq)) return; @@ -382,6 +385,9 @@ static inline void rt_queue_pull_task(struct rt_rq *rt_rq) { struct rq *rq = global_rq_of_rt_rq(rt_rq); + if (is_dl_group(rt_rq)) + return; + queue_balance_callback(rq, &per_cpu(rt_pull_head, rq->cpu), pull_rt_task); } @@ -832,6 +838,9 @@ static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags) __enqueue_rt_entity(rt_se, flags); + if (is_dl_group((rt_rq))) + return; + cpufreq_update_util(rq_of_rt_rq(rt_rq), 0); } @@ -844,6 +853,9 @@ static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags) __dequeue_rt_entity(rt_se, flags); + if (is_dl_group((rt_rq))) + return; + cpufreq_update_util(rq_of_rt_rq(rt_rq), 0); } @@ -1046,7 +1058,56 @@ static int balance_rt(struct rq *rq, struct rq_flags *rf) static void wakeup_preempt_rt(struct rq *rq, struct task_struct *p, int flags) { struct task_struct *donor = rq->donor; + struct sched_dl_entity *woken_dl_se = NULL; + struct sched_dl_entity *donor_dl_se = NULL; + + if (!rt_group_sched_enabled()) + goto same_group_sched; + /* + * Preemption checks are different if the waking task and the current donor + * are running on the global runqueue or in a cgroup. The following rules + * apply: + * - dl-tasks (and equally dl_servers) always preempt FIFO/RR tasks. + * - if donor is a FIFO/RR task inside a cgroup (i.e. run by a + * dl_server), or donor is a DEADLINE task and waking is a FIFO/RR + * task on the root cgroup, do nothing. + * - if waking is inside a cgroup but donor is a FIFO/RR task in the + * root cgroup, always reschedule. + * - if they are both on the global runqueue or in the same cgroup, run + * the standard code. + * - if they are both in a cgroup, but not the same one, check whether the + * woken task's dl_server preempts the donor's dl_server. + * - if donor is a DEADLINE task and waking is in a cgroup, check whether + * the woken task's server preempts donor. + */ + if (is_dl_group(rt_rq_of_se(&p->rt))) + woken_dl_se = dl_group_of(rt_rq_of_se(&p->rt)); + + if (task_has_dl_policy(donor)) + donor_dl_se = &donor->dl; + else if (is_dl_group(rt_rq_of_se(&donor->rt))) + donor_dl_se = dl_group_of(rt_rq_of_se(&donor->rt)); + + if (woken_dl_se != NULL && donor_dl_se != NULL) { + if (woken_dl_se == donor_dl_se) { + goto same_group_sched; + } + + if (dl_entity_preempt(woken_dl_se, donor_dl_se)) + resched_curr(rq); + + return; + + } else if (woken_dl_se != NULL) { + resched_curr(rq); + return; + + } else if (donor_dl_se != NULL) { + return; + } + +same_group_sched: /* * XXX If we're preempted by DL, queue a push? */ @@ -1071,7 +1132,8 @@ static void wakeup_preempt_rt(struct rq *rq, struct task_struct *p, int flags) * to move current somewhere else, making room for our non-migratable * task. */ - if (p->prio == donor->prio && !test_tsk_need_resched(rq->curr)) + if (!is_dl_group(rt_rq_of_se(&p->rt)) && + p->prio == donor->prio && !test_tsk_need_resched(rq->curr)) check_preempt_equal_prio(rq, p); } @@ -1384,6 +1446,9 @@ static int push_rt_rq_task(struct rt_rq *rt_rq, bool pull) struct rt_rq *lowest_rt_rq; int ret = 0; + if (is_dl_group(rt_rq)) + return 0; + if (!rt_rq->overloaded) return 0; @@ -1690,6 +1755,9 @@ static void pull_rt_rq_task(struct rt_rq *this_rt_rq) struct rq *src_rq; int rt_overload_count = rt_overloaded(this_rq); + if (is_dl_group(&this_rq->rt)) + return; + if (likely(!rt_overload_count)) return; @@ -1833,6 +1901,8 @@ static void rq_offline_rt(struct rq *rq) */ static void switched_from_rt(struct rq *rq, struct task_struct *p) { + struct rt_rq *rt_rq = rt_rq_of_se(&p->rt); + /* * If there are other RT tasks then we will reschedule * and the scheduling of the other RT tasks will handle @@ -1840,10 +1910,10 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p) * we may need to handle the pulling of RT tasks * now. */ - if (!task_on_rq_queued(p) || rq->rt.rt_nr_running) + if (!task_on_rq_queued(p) || rt_rq->rt_nr_running) return; - rt_queue_pull_task(rt_rq_of_se(&p->rt)); + rt_queue_pull_task(rt_rq); } void __init init_sched_rt_class(void) @@ -1880,6 +1950,7 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p) if (task_on_rq_queued(p)) { if (p->nr_cpus_allowed > 1 && rt_rq_of_se(&p->rt)->overloaded) rt_queue_push_tasks(rt_rq_of_se(&p->rt)); + if (p->prio < rq->donor->prio && cpu_online(cpu_of(rq))) resched_curr(rq); } @@ -1892,6 +1963,8 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p) static void prio_changed_rt(struct rq *rq, struct task_struct *p, u64 oldprio) { + struct rt_rq *rt_rq = rt_rq_of_se(&p->rt); + if (!task_on_rq_queued(p)) return; @@ -1904,15 +1977,24 @@ prio_changed_rt(struct rq *rq, struct task_struct *p, u64 oldprio) * may need to pull tasks to this runqueue. */ if (oldprio < p->prio) - rt_queue_pull_task(rt_rq_of_se(&p->rt)); + rt_queue_pull_task(rt_rq); /* * If there's a higher priority task waiting to run * then reschedule. */ - if (p->prio > rq->rt.highest_prio.curr) + if (p->prio > rt_rq->highest_prio.curr) resched_curr(rq); } else { + /* + * This task is not running, thus we check against the currently + * running task for preemption. We can preempt only if both tasks are + * in the same cgroup or on the global runqueue. + */ + if (rt_group_sched_enabled() && + rt_rq->tg != rt_rq_of_se(&rq->curr->rt)->tg) + return; + /* * This task is not running, but if it is * greater than the current running task @@ -2005,7 +2087,19 @@ static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task) #ifdef CONFIG_SCHED_CORE static int task_is_throttled_rt(struct task_struct *p, int cpu) { +#ifdef CONFIG_RT_GROUP_SCHED + struct rt_rq *rt_rq; + + rt_rq = task_group(p)->rt_rq[cpu]; + WARN_ON(!rt_group_sched_enabled() && rt_rq->tg != &root_task_group); + + if (is_dl_group(rt_rq)) + return dl_group_of(rt_rq)->dl_throttled; + else + return 0; +#else return 0; +#endif } #endif /* CONFIG_SCHED_CORE */ @@ -2244,10 +2338,10 @@ long sched_group_rt_period(struct task_group *tg) return rt_period_us; } -int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk) +int sched_rt_can_attach(struct task_group *tg) { /* Don't accept real-time tasks when there is no way for them to run */ - if (rt_group_sched_enabled() && rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0) + if (rt_group_sched_enabled() && tg->dl_bandwidth.dl_runtime == 0) return 0; return 1; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 0166e75c7733..ef11619cfc30 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -603,7 +603,7 @@ extern int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us) extern int sched_group_set_rt_period(struct task_group *tg, u64 rt_period_us); extern long sched_group_rt_runtime(struct task_group *tg); extern long sched_group_rt_period(struct task_group *tg); -extern int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk); +extern int sched_rt_can_attach(struct task_group *tg); extern struct task_group *sched_create_group(struct task_group *parent); extern void sched_online_group(struct task_group *tg, diff --git a/kernel/sched/syscalls.c b/kernel/sched/syscalls.c index 02688e75a8bd..8ed4a948b14d 100644 --- a/kernel/sched/syscalls.c +++ b/kernel/sched/syscalls.c @@ -606,6 +606,18 @@ int __sched_setscheduler(struct task_struct *p, change: if (user) { + /* + * Do not allow real-time tasks into groups that have no runtime + * assigned. + */ + if (rt_group_sched_enabled() && + dl_bandwidth_enabled() && rt_policy(policy) && + !sched_rt_can_attach(task_group(p)) && + !task_group_is_autogroup(task_group(p))) { + retval = -EPERM; + goto unlock; + } + if (dl_bandwidth_enabled() && dl_policy(policy) && !(attr->sched_flags & SCHED_FLAG_SUGOV)) { cpumask_t *span = rq->rd->span; -- 2.56.0