[RFC][PATCH 1/3] cpuidle governor API changes

[Adam Belay <abelay@novell.com>]

This patch prepares cpuidle for the menu governor.  It adds an optional
stage after idle state entry to give the governor an opportunity to
check why the state was exited.  Also it makes sure the idle loop
returns after each state entry, allowing the appropriate dynticks code
to run.

Thanks,
Adam

 drivers/cpuidle/cpuidle.c          |   33 ++++++++++++++-------------------
 drivers/cpuidle/governor.c         |    2 +-
 drivers/cpuidle/governors/ladder.c |    2 +-
 include/linux/cpuidle.h            |    4 ++--
 4 files changed, 18 insertions(+), 23 deletions(-)


diff -urN a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
--- a/drivers/cpuidle/cpuidle.c	2007-03-23 23:09:45.000000000 -0400
+++ b/drivers/cpuidle/cpuidle.c	2007-03-24 00:22:09.000000000 -0400
@@ -30,12 +30,10 @@
  * cpuidle_idle_call - the main idle loop
  *
  * NOTE: no locks or semaphores should be used here
- * FIXME: DYNTICKS handling
  */
 static void cpuidle_idle_call(void)
 {
 	struct cpuidle_device *dev = &__get_cpu_var(cpuidle_devices);
-
 	struct cpuidle_state *target_state;
 	int next_state;
 
@@ -46,24 +44,21 @@
 		return;
 	}
 
-	if (cpuidle_curr_governor->prepare_idle)
-		cpuidle_curr_governor->prepare_idle(dev);
-
-	while(!need_resched()) {
-		next_state = cpuidle_curr_governor->select_state(dev);
-		if (need_resched())
-			break;
-
-		target_state = &dev->states[next_state];
-
-		dev->last_residency = target_state->enter(dev, target_state);
-		dev->last_state = target_state;
-		target_state->time += dev->last_residency;
-		target_state->usage++;
+	/* ask the governor for the next state */
+	next_state = cpuidle_curr_governor->select(dev);
+	if (need_resched())
+		return;
+	target_state = &dev->states[next_state];
 
-		if (dev->status != CPUIDLE_STATUS_DOIDLE)
-			break;
-	}
+	/* enter the state and update stats */
+	dev->last_residency = target_state->enter(dev, target_state);
+	dev->last_state = target_state;
+	target_state->time += dev->last_residency;
+	target_state->usage++;
+
+	/* give the governor an opportunity to reflect on the outcome */
+	if (cpuidle_curr_governor->reflect)
+		cpuidle_curr_governor->reflect(dev);
 }
 
 /**
diff -urN a/drivers/cpuidle/governor.c b/drivers/cpuidle/governor.c
--- a/drivers/cpuidle/governor.c	2007-03-23 23:09:45.000000000 -0400
+++ b/drivers/cpuidle/governor.c	2007-03-24 00:31:04.000000000 -0400
@@ -124,7 +124,7 @@
 {
 	int ret = -EEXIST;
 
-	if (!gov || !gov->select_state)
+	if (!gov || !gov->select)
 		return -EINVAL;
 
 	mutex_lock(&cpuidle_lock);
diff -urN a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
--- a/drivers/cpuidle/governors/ladder.c	2007-03-23 23:09:45.000000000 -0400
+++ b/drivers/cpuidle/governors/ladder.c	2007-03-23 23:26:06.000000000 -0400
@@ -202,7 +202,7 @@
 	.init =		ladder_init_device,
 	.exit =		ladder_exit_device,
 	.scan =		ladder_scan_device,
-	.select_state =	ladder_select_state,
+	.select =	ladder_select_state,
 	.owner =	THIS_MODULE,
 };
 
diff -urN a/include/linux/cpuidle.h b/include/linux/cpuidle.h
--- a/include/linux/cpuidle.h	2007-03-23 23:09:46.000000000 -0400
+++ b/include/linux/cpuidle.h	2007-03-23 23:24:02.000000000 -0400
@@ -158,8 +158,8 @@
 	void (*exit)		(struct cpuidle_device *dev);
 	void (*scan)		(struct cpuidle_device *dev);
 
-	void (*prepare_idle)	(struct cpuidle_device *dev);
-	int  (*select_state)	(struct cpuidle_device *dev);
+	int  (*select)		(struct cpuidle_device *dev);
+	void (*reflect)		(struct cpuidle_device *dev);
 
 	struct module 		*owner;
 };