[RFC PATCH 05/12] housekeeping: Use its own static key

[Frederic Weisbecker]

Housekeeping code still depends on nohz_full static key. Since we want
to decouple housekeeping from nohz, let's create a housekeeping own static
key. It's mostly relevant for calls to is_housekeeping_cpu() from the
scheduler.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Wanpeng Li <kernellwp@xxxxxxxxx>
Cc: Luiz Capitulino <lcapitulino@xxxxxxxxxx>
---
 include/linux/housekeeping.h |  3 ++-
 kernel/housekeeping.c        | 14 +++++++++-----
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index 31a1401..cbe8d63 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.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;
diff --git a/kernel/housekeeping.c b/kernel/housekeeping.c
index 0183e75..f8be7e6 100644
--- a/kernel/housekeeping.c
+++ b/kernel/housekeeping.c
@@ -9,12 +9,15 @@
 #include <linux/housekeeping.h>
 #include <linux/tick.h>
 #include <linux/init.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();
@@ -22,7 +25,7 @@ int housekeeping_any_cpu(void)
 
 const struct cpumask *housekeeping_cpumask(void)
 {
-	if (tick_nohz_full_enabled())
+	if (static_branch_unlikely(&housekeeping_overriden))
 		return housekeeping_mask;
 
 	return cpu_possible_mask;
@@ -30,19 +33,18 @@ const struct cpumask *housekeeping_cpumask(void)
 
 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);
 }
 
 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;
 }
 
-
 void __init housekeeping_init(void)
 {
 	if (!tick_nohz_full_enabled())
@@ -58,6 +60,8 @@ 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));
 }
-- 
2.7.4