sched/isolation: Use its own static key

Housekeeping code still depends on the nohz_full static key. Since we want
to decouple housekeeping from NOHZ, let's create a housekeeping specific
static key.

It's mostly relevant for calls to is_housekeeping_cpu() from the scheduler.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509072159-31808-6-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched/isolation.h

@@ -6,6 +6,7 @@
 #include <linux/tick.h>
 
 #ifdef CONFIG_NO_HZ_FULL
+DECLARE_STATIC_KEY_FALSE(housekeeping_overriden);
 extern int housekeeping_any_cpu(void);
 extern const struct cpumask *housekeeping_cpumask(void);
 extern void housekeeping_affine(struct task_struct *t);
@@ -31,7 +32,7 @@ static inline void housekeeping_init(void) { }
 static inline bool is_housekeeping_cpu(int cpu)
 {
 #ifdef CONFIG_NO_HZ_FULL
-	if (tick_nohz_full_enabled())
+	if (static_branch_unlikely(&housekeeping_overriden))
 		return housekeeping_test_cpu(cpu);
 #endif
 	return true;

kernel/sched/isolation.c

@@ -10,12 +10,15 @@
 #include <linux/tick.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/static_key.h>
 
+DEFINE_STATIC_KEY_FALSE(housekeeping_overriden);
+EXPORT_SYMBOL_GPL(housekeeping_overriden);
 static cpumask_var_t housekeeping_mask;
 
 int housekeeping_any_cpu(void)
 {
-	if (tick_nohz_full_enabled())
+	if (static_branch_unlikely(&housekeeping_overriden))
 		return cpumask_any_and(housekeeping_mask, cpu_online_mask);
 
 	return smp_processor_id();
@@ -24,7 +27,7 @@ EXPORT_SYMBOL_GPL(housekeeping_any_cpu);
 
 const struct cpumask *housekeeping_cpumask(void)
 {
-	if (tick_nohz_full_enabled())
+	if (static_branch_unlikely(&housekeeping_overriden))
 		return housekeeping_mask;
 
 	return cpu_possible_mask;
@@ -33,14 +36,14 @@ EXPORT_SYMBOL_GPL(housekeeping_cpumask);
 
 void housekeeping_affine(struct task_struct *t)
 {
-	if (tick_nohz_full_enabled())
+	if (static_branch_unlikely(&housekeeping_overriden))
 		set_cpus_allowed_ptr(t, housekeeping_mask);
 }
 EXPORT_SYMBOL_GPL(housekeeping_affine);
 
 bool housekeeping_test_cpu(int cpu)
 {
-	if (tick_nohz_full_enabled())
+	if (static_branch_unlikely(&housekeeping_overriden))
 		return cpumask_test_cpu(cpu, housekeeping_mask);
 
 	return true;
@@ -62,6 +65,8 @@ void __init housekeeping_init(void)
 	cpumask_andnot(housekeeping_mask,
 		       cpu_possible_mask, tick_nohz_full_mask);
 
+	static_branch_enable(&housekeeping_overriden);
+
 	/* We need at least one CPU to handle housekeeping work */
 	WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
 }