pm_qos_requirement-fix
Add a raw_spinlock_t for target. target is modified in pm_qos_requirement
called by idle so it cannot be allowed to sleep.

Signed-off-by: John Kacur <jkacur at gmail dot com>
Signed-off-by: mark gross <mgross@linux.intel.com>

Index: linux-2.6.26.1-rt1.jk/kernel/pm_qos_params.c
===================================================================
--- linux-2.6.26.1-rt1.jk.orig/kernel/pm_qos_params.c
+++ linux-2.6.26.1-rt1.jk/kernel/pm_qos_params.c
@@ -42,9 +42,10 @@
 #include <linux/uaccess.h>
 
 /*
- * locking rule: all changes to target_value or requirements or notifiers lists
+ * locking rule: all changes to requirements or notifiers lists
  * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
- * held, taken with _irqsave.  One lock to rule them all
+ * held, taken with _irqsave. target is locked by pm_qos_rawlock because it
+ * is modified in pm_qos_requirement called from idle and cannot sleep.
  */
 struct requirement_list {
 	struct list_head list;
@@ -111,6 +112,7 @@ static struct pm_qos_object *pm_qos_arra
 };
 
 static DEFINE_SPINLOCK(pm_qos_lock);
+static DEFINE_RAW_SPINLOCK(pm_qos_rawlock);
 
 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 		size_t count, loff_t *f_pos);
@@ -149,13 +151,15 @@ static void update_target(int target)
 		extreme_value = pm_qos_array[target]->comparitor(
 				extreme_value, node->value);
 	}
+	spin_unlock_irqrestore(&pm_qos_lock, flags);
+	spin_lock_irqsave(&pm_qos_rawlock, flags);
 	if (pm_qos_array[target]->target_value != extreme_value) {
 		call_notifier = 1;
 		pm_qos_array[target]->target_value = extreme_value;
 		pr_debug(KERN_ERR "new target for qos %d is %d\n", target,
 			pm_qos_array[target]->target_value);
 	}
-	spin_unlock_irqrestore(&pm_qos_lock, flags);
+	spin_unlock_irqrestore(&pm_qos_rawlock, flags);
 
 	if (call_notifier)
 		blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
@@ -195,9 +199,12 @@ int pm_qos_requirement(int pm_qos_class)
 	int ret_val;
 	unsigned long flags;
 
-	spin_lock_irqsave(&pm_qos_lock, flags);
+	/*
+	 * pm_qos_requirement is called from idle, so it cannot sleep
+	 */
+	spin_lock_irqsave(&pm_qos_rawlock, flags);
 	ret_val = pm_qos_array[pm_qos_class]->target_value;
-	spin_unlock_irqrestore(&pm_qos_lock, flags);
+	spin_unlock_irqrestore(&pm_qos_rawlock, flags);
 
 	return ret_val;
 }