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authorWill Deacon <will@kernel.org>2021-07-30 12:24:30 +0100
committerPeter Zijlstra <peterz@infradead.org>2021-08-20 12:32:59 +0200
commit431c69fac05baa7477d61a44f2708e069f2bed6c (patch)
tree0a9b5e92c190187b22999f9065cb664408da5ffb /kernel/cgroup
parentd4b96fb92ae7fe7533e11e662504d96161928575 (diff)
cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus()
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. Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com> Link: https://lkml.kernel.org/r/20210730112443.23245-4-will@kernel.org
Diffstat (limited to 'kernel/cgroup')
-rw-r--r--kernel/cgroup/cpuset.c43
1 files changed, 26 insertions, 17 deletions
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index a8693783f385..391813245cb2 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -372,18 +372,29 @@ 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)) {
+ const struct cpumask *possible_mask = task_cpu_possible_mask(tsk);
+ struct cpuset *cs;
+
+ if (WARN_ON(!cpumask_and(pmask, possible_mask, cpu_online_mask)))
+ cpumask_copy(pmask, cpu_online_mask);
+
+ rcu_read_lock();
+ cs = task_cs(tsk);
+
+ while (!cpumask_intersects(cs->effective_cpus, pmask)) {
cs = parent_cs(cs);
if (unlikely(!cs)) {
/*
@@ -393,11 +404,13 @@ 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;
+ goto out_unlock;
}
}
- cpumask_and(pmask, cs->effective_cpus, cpu_online_mask);
+ cpumask_and(pmask, pmask, cs->effective_cpus);
+
+out_unlock:
+ rcu_read_unlock();
}
/*
@@ -2199,15 +2212,13 @@ 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
@@ -3302,9 +3313,7 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
unsigned long flags;
spin_lock_irqsave(&callback_lock, flags);
- rcu_read_lock();
- guarantee_online_cpus(task_cs(tsk), pmask);
- rcu_read_unlock();
+ guarantee_online_cpus(tsk, pmask);
spin_unlock_irqrestore(&callback_lock, flags);
}