sched / idle: Call default_idle_call() from cpuidle_enter_state()

The check of the cpuidle_enter() return value against -EBUSY
made in call_cpuidle() will not be necessary any more if
cpuidle_enter_state() calls default_idle_call() directly when it
is about to return -EBUSY, so make that happen and eliminate the
check.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Tested-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Kevin Hilman <khilman@linaro.org>

drivers/cpuidle/cpuidle.c

@@ -167,8 +167,10 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
 	 * local timer will be shut down.  If a local timer is used from another
 	 * CPU as a broadcast timer, this call may fail if it is not available.
 	 */
-	if (broadcast && tick_broadcast_enter())
+	if (broadcast && tick_broadcast_enter()) {
+		default_idle_call();
 		return -EBUSY;
+	}
 
 	/* Take note of the planned idle state. */
 	sched_idle_set_state(target_state);

include/linux/cpuidle.h

@@ -202,6 +202,7 @@ static inline struct cpuidle_driver *cpuidle_get_cpu_driver(
 
 /* kernel/sched/idle.c */
 extern void sched_idle_set_state(struct cpuidle_state *idle_state);
+extern void default_idle_call(void);
 
 #ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
 void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev, atomic_t *a);

kernel/sched/idle.c

@@ -76,12 +76,13 @@ void __weak arch_cpu_idle(void)
 	local_irq_enable();
 }
 
-static void default_idle_call(void)
+/**
+ * default_idle_call - Default CPU idle routine.
+ *
+ * To use when the cpuidle framework cannot be used.
+ */
+void default_idle_call(void)
 {
-	/*
-	 * We can't use the cpuidle framework, let's use the default idle
-	 * routine.
-	 */
 	if (current_clr_polling_and_test())
 		local_irq_enable();
 	else
@@ -91,8 +92,6 @@ static void default_idle_call(void)
 static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		      int next_state)
 {
-	int entered_state;
-
 	/* Fall back to the default arch idle method on errors. */
 	if (next_state < 0) {
 		default_idle_call();
@@ -114,12 +113,7 @@ static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 	 * This function will block until an interrupt occurs and will take
 	 * care of re-enabling the local interrupts
 	 */
-	entered_state = cpuidle_enter(drv, dev, next_state);
-
-	if (entered_state == -EBUSY)
-		default_idle_call();
-
-	return entered_state;
+	return cpuidle_enter(drv, dev, next_state);
 }
 
 /**