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Thu, 11 Jun 2026 01:42:57 -0700 (PDT) Received: from jlelli-thinkpadt14gen4.remote.csb ([151.29.95.181]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4601f2f5612sm77250977f8f.15.2026.06.11.01.42.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Jun 2026 01:42:57 -0700 (PDT) Date: Thu, 11 Jun 2026 10:42:55 +0200 From: Juri Lelli To: Yuri Andriaccio Cc: Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Tejun Heo , Johannes Weiner , Michal =?iso-8859-1?Q?Koutn=FD?= , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Luca Abeni , Yuri Andriaccio Subject: Re: [RFC PATCH v6 12/25] sched/rt: Add {alloc/unregister/free}_rt_sched_group Message-ID: References: <20260608121546.69910-1-yurand2000@gmail.com> <20260608121546.69910-13-yurand2000@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260608121546.69910-13-yurand2000@gmail.com> Hello, On 08/06/26 14:15, Yuri Andriaccio wrote: > Add allocation and deallocation code for rt-cgroups. > > Declare dl_server specific functions (only skeleton, but no > implementation yet), needed by the deadline servers to be called when > trying to schedule. > > Initialize a cgroup's active context to that of its parent. > > 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 > --- ... > void free_rt_sched_group(struct task_group *tg) > { > + int i; > + unsigned long flags; > + > if (!rt_group_sched_enabled()) > return; > + > + if (!tg->dl_se || !tg->rt_rq) > + return; > + > + for_each_possible_cpu(i) { > + if (!tg->dl_se[i] || !tg->rt_rq[i]) > + continue; > + > + /* > + * Shutdown the dl_server and free it > + * > + * Since the dl timer is going to be cancelled, > + * we risk to never decrease the running bw... > + * Fix this issue by changing the group runtime > + * to 0 immediately before freeing it. > + */ > + if (tg->dl_se[i]->dl_runtime) > + dl_init_tg(tg->dl_se[i], 0, tg->dl_se[i]->dl_period); > + > + raw_spin_rq_lock_irqsave(cpu_rq(i), flags); > + hrtimer_cancel(&tg->dl_se[i]->dl_timer); > + raw_spin_rq_unlock_irqrestore(cpu_rq(i), flags); Why do we need to grab rq lock here? I actually fear this can deadlock with the timer callback. > + kfree(tg->dl_se[i]); > + > + /* Free the local per-cpu runqueue */ > + kfree(rq_of_rt_rq(tg->rt_rq[i])); > + } > + > + kfree(tg->rt_rq); > + kfree(tg->dl_se); > } > > +static inline void __rt_rq_free(struct rt_rq **rt_rq) > +{ > + int i; > + > + for_each_possible_cpu(i) { > + kfree(rq_of_rt_rq(rt_rq[i])); ^^ Can this result in NULL pointer deref if __alloc_rt_sched_group_data() fails for some reason midway in the CPU loop? > + } > + > + kfree(rt_rq); > +} > + > +DEFINE_FREE(rt_rq_free, struct rt_rq **, if (_T) __rt_rq_free(_T)) > + > +static inline void __dl_se_free(struct sched_dl_entity **dl_se) > +{ > + int i; > + > + for_each_possible_cpu(i) { > + kfree(dl_se[i]); > + } > + > + kfree(dl_se); > +} > + > +DEFINE_FREE(dl_se_free, struct sched_dl_entity **, if (_T) __dl_se_free(_T)) > + > +static int __alloc_rt_sched_group_data(struct task_group *tg) { > + /* Instantiate automatic cleanup in event of kalloc fail */ > + struct rt_rq **tg_rt_rq __free(rt_rq_free) = NULL; > + struct sched_dl_entity **tg_dl_se __free(dl_se_free) = NULL; > + struct sched_dl_entity *dl_se __free(kfree) = NULL; > + struct rq *s_rq __free(kfree) = NULL; > + int i; > + > + tg_rt_rq = kcalloc(nr_cpu_ids, sizeof(struct rt_rq *), GFP_KERNEL); > + if (!tg_rt_rq) > + return 0; > + > + tg_dl_se = kcalloc(nr_cpu_ids, > + sizeof(struct sched_dl_entity *), GFP_KERNEL); > + if (!tg_dl_se) > + return 0; > + > + for_each_possible_cpu(i) { > + s_rq = kzalloc_node(sizeof(struct rq), > + GFP_KERNEL, cpu_to_node(i)); > + if (!s_rq) > + return 0; > + > + dl_se = kzalloc_node(sizeof(struct sched_dl_entity), > + GFP_KERNEL, cpu_to_node(i)); > + if (!dl_se) > + return 0; > + > + tg_rt_rq[i] = &no_free_ptr(s_rq)->rt; > + tg_dl_se[i] = no_free_ptr(dl_se); > + } > + > + tg->rt_rq = no_free_ptr(tg_rt_rq); > + tg->dl_se = no_free_ptr(tg_dl_se); > + > + return 1; > +} ... Thanks, Juri