linux-kernel - [PATCH v3 4/4] cgroup/cpuset: Make cpuset_attach_task() skip subpartitions CPUs for top

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Message-Id: <20230406140404.2718574-5-longman@redhat.com>
Date:   Thu,  6 Apr 2023 10:04:04 -0400
From:   Waiman Long <longman@...hat.com>
To:     Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Christian Brauner <brauner@...nel.org>
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Michal Koutný <mkoutny@...e.com>,
        gscrivan@...hat.com, Waiman Long <longman@...hat.com>
Subject: [PATCH v3 4/4] cgroup/cpuset: Make cpuset_attach_task() skip subpartitions CPUs for top_cpuset

It is found that attaching a task to the top_cpuset does not currently
ignore CPUs allocated to subpartitions in cpuset_attach_task(). So the
code is changed to fix that.

Signed-off-by: Waiman Long <longman@...hat.com>
Reviewed-by: Michal Koutný <mkoutny@...e.com>
---
 kernel/cgroup/cpuset.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index a331e11e3d20..8fd90f7bdeb0 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2540,7 +2540,8 @@ static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task)
 	if (cs != &top_cpuset)
 		guarantee_online_cpus(task, cpus_attach);
 	else
-		cpumask_copy(cpus_attach, task_cpu_possible_mask(task));
+		cpumask_andnot(cpus_attach, task_cpu_possible_mask(task),
+			       cs->subparts_cpus);
 	/*
 	 * can_attach beforehand should guarantee that this doesn't
 	 * fail.  TODO: have a better way to handle failure here
-- 
2.31.1