Re: [RFC][PATCH 8/8] sched,idle: Reflow cpuidle_idle_call()

[Peter Zijlstra <peterz@infradead.org>]

On Mon, Apr 14, 2014 at 10:59:11AM +0200, Peter Zijlstra wrote:
> > Why not using braces here and moving the use_default code block inside 
> > it instead?
> 
> I didn't because there's two goto use_default sites, but sure, I can do
> that.

---
Subject: sched,idle: Reflow cpuidle_idle_call()
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri Apr 11 13:55:48 CEST 2014

Apply goto to reduce lines and nesting levels.

Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-xt260n72av3ip7jsaef2ps3h@git.kernel.org
---
 kernel/sched/idle.c |  131 +++++++++++++++++++++++-----------------------------
 1 file changed, 58 insertions(+), 73 deletions(-)

--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -73,7 +73,7 @@ static int cpuidle_idle_call(void)
 {
 	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
-	int next_state, entered_state, ret;
+	int next_state, entered_state;
 	bool broadcast;
 
 	/*
@@ -102,90 +102,75 @@ static int cpuidle_idle_call(void)
 	 * Check if the cpuidle framework is ready, otherwise fallback
 	 * to the default arch specific idle method
 	 */
-	ret = cpuidle_enabled(drv, dev);
-
-	if (!ret) {
-		/*
-		 * Ask the governor to choose an idle state it thinks
-		 * it is convenient to go to. There is *always* a
-		 * convenient idle state
-		 */
-		next_state = cpuidle_select(drv, dev);
-
+	if (cpuidle_enabled(drv, dev)) {
+use_default:
 		/*
-		 * The idle task must be scheduled, it is pointless to
-		 * go to idle, just update no idle residency and get
-		 * out of this function
+		 * We can't use the cpuidle framework, let's use the default
+		 * idle routine.
 		 */
-		if (current_clr_polling_and_test()) {
-			dev->last_residency = 0;
-			entered_state = next_state;
+		if (current_clr_polling_and_test())
 			local_irq_enable();
-		} else {
-			broadcast = !!(drv->states[next_state].flags &
-				       CPUIDLE_FLAG_TIMER_STOP);
-
-			if (broadcast) {
-				/*
-				 * Tell the time framework to switch
-				 * to a broadcast timer because our
-				 * local timer will be shutdown. If a
-				 * local timer is used from another
-				 * cpu as a broadcast timer, this call
-				 * may fail if it is not available
-				 */
-				ret = clockevents_notify(
-					CLOCK_EVT_NOTIFY_BROADCAST_ENTER,
-					&dev->cpu);
-			}
-
-			if (!ret) {
-				trace_cpu_idle_rcuidle(next_state, dev->cpu);
-
-				/*
-				 * Enter the idle state previously
-				 * returned by the governor
-				 * decision. 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);
-
-				trace_cpu_idle_rcuidle(PWR_EVENT_EXIT,
-						       dev->cpu);
-
-				if (broadcast)
-					clockevents_notify(
-						CLOCK_EVT_NOTIFY_BROADCAST_EXIT,
-						&dev->cpu);
-
-				/*
-				 * Give the governor an opportunity to reflect on the
-				 * outcome
-				 */
-				cpuidle_reflect(dev, entered_state);
-			}
-		}
+		else
+			arch_cpu_idle();
+
+		goto exit_idle;
 	}
 
 	/*
-	 * We can't use the cpuidle framework, let's use the default
-	 * idle routine
+	 * Ask the governor to choose an idle state it thinks
+	 * it is convenient to go to. There is *always* a
+	 * convenient idle state
 	 */
-	if (ret) {
-		if (!current_clr_polling_and_test())
-			arch_cpu_idle();
-		else
-			local_irq_enable();
+	next_state = cpuidle_select(drv, dev);
+
+	/*
+	 * The idle task must be scheduled, it is pointless to
+	 * go to idle, just update no idle residency and get
+	 * out of this function
+	 */
+	if (current_clr_polling_and_test()) {
+		dev->last_residency = 0;
+		entered_state = next_state;
+		local_irq_enable();
+		goto exit_idle;
 	}
 
+	broadcast = !!(drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP);
+
+	/*
+	 * Tell the time framework to switch to a broadcast timer
+	 * because our local timer will be shutdown. If a local timer
+	 * is used from another cpu as a broadcast timer, this call may
+	 * fail if it is not available
+	 */
+	if (broadcast &&
+	    clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu))
+		goto use_default;
+
+	trace_cpu_idle_rcuidle(next_state, dev->cpu);
+
+	/*
+	 * Enter the idle state previously returned by the governor decision.
+	 * 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);
+
+	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
+
+	if (broadcast)
+		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu);
+
+	/*
+	 * Give the governor an opportunity to reflect on the outcome
+	 */
+	cpuidle_reflect(dev, entered_state);
+
+exit_idle:
 	__current_set_polling();
 
 	/*
-	 * It is up to the idle functions to enable back the local
-	 * interrupt
+	 * It is up to the idle functions to reenable local interrupts
 	 */
 	if (WARN_ON_ONCE(irqs_disabled()))
 		local_irq_enable();