[PATCH 3/4] nohz: add tick_nohz_full_clear_cpus() API

[<cmetcalf@ezchip.com>]

From: Chris Metcalf <cmetcalf@ezchip.com>

This is useful, for example, to modify a cpumask to avoid the
nohz cores so that interrupts aren't sent to them.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
---
Motivated by patch 4/4 in this series.

 include/linux/tick.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 9c085dc12ae9..d53ad4892a39 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -186,6 +186,12 @@ static inline bool tick_nohz_full_cpu(int cpu)
 	return cpumask_test_cpu(cpu, tick_nohz_full_mask);
 }
 
+static inline void tick_nohz_full_clear_cpus(struct cpumask *mask)
+{
+	if (tick_nohz_full_enabled())
+		cpumask_andnot(mask, mask, tick_nohz_full_mask);
+}
+
 extern void __tick_nohz_full_check(void);
 extern void tick_nohz_full_kick(void);
 extern void tick_nohz_full_kick_cpu(int cpu);
@@ -194,6 +200,7 @@ extern void __tick_nohz_task_switch(struct task_struct *tsk);
 #else
 static inline bool tick_nohz_full_enabled(void) { return false; }
 static inline bool tick_nohz_full_cpu(int cpu) { return false; }
+static inline void tick_nohz_full_clear_cpus(struct cpumask *mask) { }
 static inline void __tick_nohz_full_check(void) { }
 static inline void tick_nohz_full_kick_cpu(int cpu) { }
 static inline void tick_nohz_full_kick(void) { }
-- 
2.1.2