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Date: Sat, 2 Nov 2019 00:14:06 +0000 From: Valentin Schneider <valentin.schneider@....com> To: linux-kernel@...r.kernel.org, cgroups@...r.kernel.org Cc: lizefan@...wei.com, tj@...nel.org, hannes@...xchg.org, mingo@...nel.org, peterz@...radead.org, vincent.guittot@...aro.org, Dietmar.Eggemann@....com, morten.rasmussen@....com, qperret@...gle.com, Michal Koutný <mkoutny@...e.com> Subject: [PATCH] sched/topology, cpuset: Account for housekeeping CPUs to avoid empty cpumasks Michal noted that a cpuset's effective_cpus can be a non-empy mask, but because of the masking done with housekeeping_cpumask(HK_FLAG_DOMAIN) further down the line, we can still end up with an empty cpumask being passed down to partition_sched_domains_locked(). Do the proper thing and don't just check the mask is non-empty - check that its intersection with housekeeping_cpumask(HK_FLAG_DOMAIN) is non-empty. Fixes: cd1cb3350561 ("sched/topology: Don't try to build empty sched domains") Reported-by: Michal Koutný <mkoutny@...e.com> Signed-off-by: Valentin Schneider <valentin.schneider@....com> --- kernel/cgroup/cpuset.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index c87ee6412b36..e4c10785dc7c 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -798,9 +798,14 @@ static int generate_sched_domains(cpumask_var_t **domains, cpumask_subset(cp->cpus_allowed, top_cpuset.effective_cpus)) continue; + /* + * Skip cpusets that would lead to an empty sched domain. + * That could be because effective_cpus is empty, or because + * it's only spanning CPUs outside the housekeeping mask. + */ if (is_sched_load_balance(cp) && - !cpumask_empty(cp->effective_cpus)) + cpumask_intersects(cp->effective_cpus, + housekeeping_cpumask(HK_FLAG_DOMAIN))) csa[csn++] = cp; /* skip @cp's subtree if not a partition root */ -- 2.22.0
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