linux-kernel - [PATCH-cgroup 1/2] cgroup/cpuset: Account for boot time isolated CPUs

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Message-ID: <20240820195536.202066-2-longman@redhat.com>
Date: Tue, 20 Aug 2024 15:55:35 -0400
From: Waiman Long <longman@...hat.com>
To: Tejun Heo <tj@...nel.org>,
	Zefan Li <lizefan.x@...edance.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Koutný <mkoutny@...e.com>,
	Shuah Khan <shuah@...nel.org>
Cc: cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	Waiman Long <longman@...hat.com>
Subject: [PATCH-cgroup 1/2] cgroup/cpuset: Account for boot time isolated CPUs

With the "isolcpus" boot command line parameter, we are able to
create isolated CPUs at boot time. These isolated CPUs aren't fully
accounted for in the cpuset code. For instance, the root cgroup's
"cpuset.cpus.isolated" control file does not include the boot time
isolated CPUs. Fix that by looking for pre-isolated CPUs at init time.

The prstate_housekeeping_conflict() function does check the
HK_TYPE_DOMAIN housekeeping cpumask to make sure that CPUs outside of it
can only be used in isolated partition. Given the fact that we are going
to make housekeeping cpumasks dynamic, the current check may not be right
anymore. Save the boot time HK_TYPE_DOMAIN cpumask and check against
it instead of the upcoming dynamic HK_TYPE_DOMAIN housekeeping cpumask.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 kernel/cgroup/cpuset.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 7db55eed63cf..8b40df89c3c1 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -224,6 +224,12 @@ static cpumask_var_t	subpartitions_cpus;
  */
 static cpumask_var_t	isolated_cpus;
 
+/*
+ * Housekeeping (HK_TYPE_DOMAIN) CPUs at boot
+ */
+static cpumask_var_t	boot_hk_cpus;
+static bool		have_boot_isolcpus;
+
 /* List of remote partition root children */
 static struct list_head remote_children;
 
@@ -1823,15 +1829,15 @@ static void remote_partition_check(struct cpuset *cs, struct cpumask *newmask,
  * @new_cpus: cpu mask
  * Return: true if there is conflict, false otherwise
  *
- * CPUs outside of housekeeping_cpumask(HK_TYPE_DOMAIN) can only be used in
- * an isolated partition.
+ * CPUs outside of boot_hk_cpus, if defined, can only be used in an
+ * isolated partition.
  */
 static bool prstate_housekeeping_conflict(int prstate, struct cpumask *new_cpus)
 {
-	const struct cpumask *hk_domain = housekeeping_cpumask(HK_TYPE_DOMAIN);
-	bool all_in_hk = cpumask_subset(new_cpus, hk_domain);
+	if (!have_boot_isolcpus)
+		return false;
 
-	if (!all_in_hk && (prstate != PRS_ISOLATED))
+	if ((prstate != PRS_ISOLATED) && !cpumask_subset(new_cpus, boot_hk_cpus))
 		return true;
 
 	return false;
@@ -4345,6 +4351,13 @@ int __init cpuset_init(void)
 
 	BUG_ON(!alloc_cpumask_var(&cpus_attach, GFP_KERNEL));
 
+	have_boot_isolcpus = housekeeping_enabled(HK_TYPE_DOMAIN);
+	if (have_boot_isolcpus) {
+		BUG_ON(!alloc_cpumask_var(&boot_hk_cpus, GFP_KERNEL));
+		cpumask_copy(boot_hk_cpus, housekeeping_cpumask(HK_TYPE_DOMAIN));
+		cpumask_andnot(isolated_cpus, cpu_possible_mask, boot_hk_cpus);
+	}
+
 	return 0;
 }
 
-- 
2.43.5