[PATCH 3/4] sched/isolation: Infrastructure to support rcu nocb cpumask changes

[Frederic Weisbecker <frederic@kernel.org>]

Provide a minimal infrastructure to change the housekeeping cpumasks.
For now only RCU NOCB cpumask is handled.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Phil Auld <pauld@redhat.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
---
 include/linux/sched/isolation.h | 13 +++++++++++
 kernel/sched/isolation.c        | 38 +++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index 8c15abd67aed..c6d0e3f83a20 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -25,6 +25,8 @@ extern const struct cpumask *housekeeping_cpumask(enum hk_type type);
 extern bool housekeeping_enabled(enum hk_type type);
 extern void housekeeping_affine(struct task_struct *t, enum hk_type type);
 extern bool housekeeping_test_cpu(int cpu, enum hk_type type);
+extern int housekeeping_cpumask_set(struct cpumask *cpumask, enum hk_type type);
+extern int housekeeping_cpumask_clear(struct cpumask *cpumask, enum hk_type type);
 extern void __init housekeeping_init(void);
 
 #else
@@ -46,6 +48,17 @@ static inline bool housekeeping_enabled(enum hk_type type)
 
 static inline void housekeeping_affine(struct task_struct *t,
 				       enum hk_type type) { }
+
+static inline int housekeeping_cpumask_set(struct cpumask *cpumask, enum hk_type type)
+{
+	return -EINVAL;
+}
+
+static inline int housekeeping_cpumask_clear(struct cpumask *cpumask, enum hk_type type)
+{
+	return -EINVAL;
+}
+
 static inline void housekeeping_init(void) { }
 #endif /* CONFIG_CPU_ISOLATION */
 
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 373d42c707bc..ab4aba795c01 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -79,6 +79,44 @@ bool housekeeping_test_cpu(int cpu, enum hk_type type)
 }
 EXPORT_SYMBOL_GPL(housekeeping_test_cpu);
 
+static int housekeeping_cpumask_update(struct cpumask *cpumask,
+				       enum hk_type type, bool on)
+{
+	int err;
+
+	switch (type) {
+	case HK_TYPE_RCU:
+		err = rcu_nocb_cpumask_update(cpumask, on);
+		break;
+	default:
+		err = -EINVAL;
+	}
+
+	if (err >= 0) {
+		if (on) {
+			cpumask_or(housekeeping.cpumasks[type],
+				   housekeeping.cpumasks[type],
+				   cpumask);
+		} else {
+			cpumask_andnot(housekeeping.cpumasks[type],
+				       housekeeping.cpumasks[type],
+				       cpumask);
+		}
+	}
+
+	return err;
+}
+
+int housekeeping_cpumask_set(struct cpumask *cpumask, enum hk_type type)
+{
+	return housekeeping_cpumask_update(cpumask, type, true);
+}
+
+int housekeeping_cpumask_clear(struct cpumask *cpumask, enum hk_type type)
+{
+	return housekeeping_cpumask_update(cpumask, type, false);
+}
+
 void __init housekeeping_init(void)
 {
 	enum hk_type type;
-- 
2.25.1