Re: [PATCH v8 06/19] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1
From: Valentin Schneider <hidden>
Date: 2021-06-04 17:11:11
Also in:
linux-arm-kernel, lkml
On 02/06/21 17:47, Will Deacon wrote:
quoted hunk ↗ jump to hunk
@@ -3322,9 +3322,13 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask) void cpuset_cpus_allowed_fallback(struct task_struct *tsk) { + const struct cpumask *cs_mask; + const struct cpumask *possible_mask = task_cpu_possible_mask(tsk); + rcu_read_lock(); - do_set_cpus_allowed(tsk, is_in_v2_mode() ? - task_cs(tsk)->cpus_allowed : cpu_possible_mask); + cs_mask = task_cs(tsk)->cpus_allowed; + if (is_in_v2_mode() && cpumask_subset(cs_mask, possible_mask)) + do_set_cpus_allowed(tsk, cs_mask);
Since the task will still go through the is_cpu_allowed() loop in select_fallback_rq() after this, is the subset check actually required here? It would have more merit if cpuset_cpus_allowed_fallback() returned whether it actually changed the allowed mask or not, in which case we could branch either to the is_cpu_allowed() loop (as we do unconditionally now), or to the 'state == possible' switch case.
rcu_read_unlock();
/*
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2.32.0.rc0.204.g9fa02ecfa5-goog