[RFC][PATCH 2/7] sched: power: Power driver late callback interface

[Morten Rasmussen <morten.rasmussen@arm.com>]

Adds a late callback to the power driver interface which is called
with irq enabled and no locks held. The power driver may postpone
work that can't be done in schedule context (irq disabled and rq
locks held) and let the late callback handle it.

Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
---
 include/linux/sched/power.h |    3 +++
 kernel/sched/core.c         |    1 +
 kernel/sched/fair.c         |    2 ++
 kernel/sched/power.c        |    6 ++++++
 kernel/sched/sched.h        |    8 ++++++++
 5 files changed, 20 insertions(+)

diff --git a/include/linux/sched/power.h b/include/linux/sched/power.h
index cb2cf37..aba5f47 100644
--- a/include/linux/sched/power.h
+++ b/include/linux/sched/power.h
@@ -25,6 +25,9 @@ struct power_driver {
 	int (*go_faster)	(int cpu, int hint);
 	/* Decrease cpu capacity hint */
 	int (*go_slower)	(int cpu, int hint);
+
+	/* Scheduler call-back without rq lock held and with irq enabled */
+	void (*late_callback)	(int cpu);
 };
 
 int power_driver_register(struct power_driver *driver);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 05c39f0..12b4753 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1913,6 +1913,7 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
 		put_task_struct(prev);
 	}
 
+	power_late_callback(raw_smp_processor_id());
 	tick_nohz_task_switch(current);
 }
 
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 68f1609..edba1bb 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5742,6 +5742,8 @@ static void run_rebalance_domains(struct softirq_action *h)
 	 * stopped.
 	 */
 	nohz_idle_balance(this_cpu, idle);
+
+	power_late_callback(this_cpu);
 }
 
 static inline int on_null_domain(int cpu)
diff --git a/kernel/sched/power.c b/kernel/sched/power.c
index b82965a..f70b563 100644
--- a/kernel/sched/power.c
+++ b/kernel/sched/power.c
@@ -56,3 +56,9 @@ int go_slower(int cpu, int hint)
 	return power_driver->go_slower(cpu, hint);
 }
 
+void power_late_callback(int cpu)
+{
+	if (!power_driver)
+		return;
+	power_driver->late_callback(cpu);
+}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index ef0a7b2..907a967 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1364,3 +1364,11 @@ static inline u64 irq_time_read(int cpu)
 }
 #endif /* CONFIG_64BIT */
 #endif /* CONFIG_IRQ_TIME_ACCOUNTING */
+
+#ifdef CONFIG_SCHED_POWER
+extern void power_late_callback(int cpu);
+#else
+static inline void power_late_callback(int cpu)
+{
+}
+#endif /* CONFIG_SCHED_POWER */
-- 
1.7.9.5