From: Waiman Long <longman@redhat.com>
Date: Thu, 1 Sep 2022 20:57:36 +0000 (-0400)
Subject: cgroup/cpuset: Enable update_tasks_cpumask() on top_cpuset
X-Git-Tag: v5.15.79~640
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=046803b74d510f6ea61b3890ba8a7a20120c9ef6;p=platform%2Fkernel%2Flinux-rpi.git

cgroup/cpuset: Enable update_tasks_cpumask() on top_cpuset

[ Upstream commit ec5fbdfb99d18482619ac42605cb80fbb56068ee ]

Previously, update_tasks_cpumask() is not supposed to be called with
top cpuset. With cpuset partition that takes CPUs away from the top
cpuset, adjusting the cpus_mask of the tasks in the top cpuset is
necessary. Percpu kthreads, however, are ignored.

Fixes: ee8dde0cd2ce ("cpuset: Add new v2 cpuset.sched.partition flag")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 3213d3c..428820b 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -33,6 +33,7 @@
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/kmod.h>
+#include <linux/kthread.h>
 #include <linux/list.h>
 #include <linux/mempolicy.h>
 #include <linux/mm.h>
@@ -1087,10 +1088,18 @@ static void update_tasks_cpumask(struct cpuset *cs)
 {
 	struct css_task_iter it;
 	struct task_struct *task;
+	bool top_cs = cs == &top_cpuset;
 
 	css_task_iter_start(&cs->css, 0, &it);
-	while ((task = css_task_iter_next(&it)))
+	while ((task = css_task_iter_next(&it))) {
+		/*
+		 * Percpu kthreads in top_cpuset are ignored
+		 */
+		if (top_cs && (task->flags & PF_KTHREAD) &&
+		    kthread_is_per_cpu(task))
+			continue;
 		set_cpus_allowed_ptr(task, cs->effective_cpus);
+	}
 	css_task_iter_end(&it);
 }
 
@@ -2052,12 +2061,7 @@ static int update_prstate(struct cpuset *cs, int new_prs)
 		update_flag(CS_CPU_EXCLUSIVE, cs, 0);
 	}
 
-	/*
-	 * Update cpumask of parent's tasks except when it is the top
-	 * cpuset as some system daemons cannot be mapped to other CPUs.
-	 */
-	if (parent != &top_cpuset)
-		update_tasks_cpumask(parent);
+	update_tasks_cpumask(parent);
 
 	if (parent->child_ecpus_count)
 		update_sibling_cpumasks(parent, cs, &tmpmask);