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Wysocki" , kernel-team@android.com Subject: [PATCH v6 08/21] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() Date: Tue, 18 May 2021 10:47:12 +0100 Message-Id: <20210518094725.7701-9-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210518094725.7701-1-will@kernel.org> References: <20210518094725.7701-1-will@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210518_024806_745497_710347AE X-CRM114-Status: GOOD ( 19.37 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Asymmetric systems may not offer the same level of userspace ISA support across all CPUs, meaning that some applications cannot be executed by some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do not feature support for 32-bit applications on both clusters. Modify guarantee_online_cpus() to take task_cpu_possible_mask() into account when trying to find a suitable set of online CPUs for a given task. This will avoid passing an invalid mask to set_cpus_allowed_ptr() during ->attach() and will subsequently allow the cpuset hierarchy to be taken into account when forcefully overriding the affinity mask for a task which requires migration to a compatible CPU. Cc: Li Zefan Cc: Tejun Heo Cc: Johannes Weiner Signed-off-by: Will Deacon --- include/linux/cpuset.h | 2 +- kernel/cgroup/cpuset.c | 33 +++++++++++++++++++-------------- 2 files changed, 20 insertions(+), 15 deletions(-) diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index ed6ec677dd6b..414a8e694413 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -185,7 +185,7 @@ static inline void cpuset_read_unlock(void) { } static inline void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask) { - cpumask_copy(mask, cpu_possible_mask); + cpumask_copy(mask, task_cpu_possible_mask(p)); } static inline void cpuset_cpus_allowed_fallback(struct task_struct *p) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 8c799260a4a2..b532a5333ff9 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -372,18 +372,26 @@ static inline bool is_in_v2_mode(void) } /* - * Return in pmask the portion of a cpusets's cpus_allowed that - * are online. If none are online, walk up the cpuset hierarchy - * until we find one that does have some online cpus. + * Return in pmask the portion of a task's cpusets's cpus_allowed that + * are online and are capable of running the task. If none are found, + * walk up the cpuset hierarchy until we find one that does have some + * appropriate cpus. * * One way or another, we guarantee to return some non-empty subset * of cpu_online_mask. * * Call with callback_lock or cpuset_mutex held. */ -static void guarantee_online_cpus(struct cpuset *cs, struct cpumask *pmask) +static void guarantee_online_cpus(struct task_struct *tsk, + struct cpumask *pmask) { - while (!cpumask_intersects(cs->effective_cpus, cpu_online_mask)) { + struct cpuset *cs = task_cs(tsk); + const struct cpumask *possible_mask = task_cpu_possible_mask(tsk); + + if (WARN_ON(!cpumask_and(pmask, possible_mask, cpu_online_mask))) + cpumask_copy(pmask, cpu_online_mask); + + while (!cpumask_intersects(cs->effective_cpus, pmask)) { cs = parent_cs(cs); if (unlikely(!cs)) { /* @@ -393,11 +401,10 @@ static void guarantee_online_cpus(struct cpuset *cs, struct cpumask *pmask) * cpuset's effective_cpus is on its way to be * identical to cpu_online_mask. */ - cpumask_copy(pmask, cpu_online_mask); return; } } - cpumask_and(pmask, cs->effective_cpus, cpu_online_mask); + cpumask_and(pmask, pmask, cs->effective_cpus); } /* @@ -2199,15 +2206,13 @@ static void cpuset_attach(struct cgroup_taskset *tset) percpu_down_write(&cpuset_rwsem); - /* prepare for attach */ - if (cs == &top_cpuset) - cpumask_copy(cpus_attach, cpu_possible_mask); - else - guarantee_online_cpus(cs, cpus_attach); - guarantee_online_mems(cs, &cpuset_attach_nodemask_to); cgroup_taskset_for_each(task, css, tset) { + if (cs != &top_cpuset) + guarantee_online_cpus(task, cpus_attach); + else + cpumask_copy(cpus_attach, task_cpu_possible_mask(task)); /* * can_attach beforehand should guarantee that this doesn't * fail. TODO: have a better way to handle failure here @@ -3303,7 +3308,7 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask) spin_lock_irqsave(&callback_lock, flags); rcu_read_lock(); - guarantee_online_cpus(task_cs(tsk), pmask); + guarantee_online_cpus(tsk, pmask); rcu_read_unlock(); spin_unlock_irqrestore(&callback_lock, flags); } -- 2.31.1.751.gd2f1c929bd-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel