[PATCH 1/2] sched: isolation: cpu isolation handles for cpuset

[Paul Gortmaker]

Assuming we want to drive isolation from cpuset and not something
like /sys/devices/system/cpu/cpu*/hotplug/isolation then we'll
need some kind of handle for cpuset to drive it from.

These would also serve as a collection point for all the isolation
related operations - current and future.  While only RCU nocb toggle
is currently deployed, I've left some guesses at what is probably to
come in the future.

Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Valentin Schneider <valentin.schneider@xxxxxxx>
[PG: RFC code - not for merge]
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 include/linux/sched/isolation.h |  4 ++++
 kernel/sched/isolation.c        | 22 ++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index cc9f393e2a70..3ab9c667c441 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -25,6 +25,8 @@ extern bool housekeeping_enabled(enum hk_flags flags);
 extern void housekeeping_affine(struct task_struct *t, enum hk_flags flags);
 extern bool housekeeping_test_cpu(int cpu, enum hk_flags flags);
 extern void __init housekeeping_init(void);
+extern void isolate_cpu(int cpu);
+extern void deisolate_cpu(int cpu);
 
 #else
 
@@ -46,6 +48,8 @@ static inline bool housekeeping_enabled(enum hk_flags flags)
 static inline void housekeeping_affine(struct task_struct *t,
 				       enum hk_flags flags) { }
 static inline void housekeeping_init(void) { }
+static void isolate_cpu(int cpu) { }
+static void deisolate_cpu(int cpu) { }
 #endif /* CONFIG_CPU_ISOLATION */
 
 static inline bool housekeeping_cpu(int cpu, enum hk_flags flags)
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 7f06eaf12818..57b105d42632 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -63,6 +63,28 @@ bool housekeeping_test_cpu(int cpu, enum hk_flags flags)
 }
 EXPORT_SYMBOL_GPL(housekeeping_test_cpu);
 
+void isolate_cpu(int cpu)
+{
+	pr_info("Isolating core %d\n", cpu);
+	if (rcu_nocb_cpu_offload(cpu))
+		pr_warn("RCU; unable to nocb offload CPU %d\n", cpu);
+#if 0	/* TODO */
+	housekeeping_clear_cpu(cpu);
+	tick_nohz_full_add_cpus_to(cpumask_of(cpu));
+#endif
+}
+
+void deisolate_cpu(int cpu)
+{
+	pr_info("Deisolating core %d\n", cpu);
+#if 0	/* TODO */
+	tick_nohz_full_clear_cpus_from(cpumask_of(cpu));
+	housekeeping_add_cpu(cpu);
+#endif
+	if (rcu_nocb_cpu_deoffload(cpu))
+		pr_warn("RCU: unable to nocb reload CPU %d\n", cpu);
+}
+
 void __init housekeeping_init(void)
 {
 	if (!housekeeping_flags)
-- 
2.15.0