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Message-Id: <20191104003906.31476-1-valentin.schneider@arm.com>
Date: Mon, 4 Nov 2019 00:39:06 +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 v2] 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
@@ -798,8 +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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