+ pm-qos-remove-locks-around-blocking-notifier.patch added to -mm tree

[akpm@xxxxxxxxxxxxxxxxxxxx]

The patch titled
     pm-qos-remove-locks-around-blocking-notifier
has been added to the -mm tree.  Its filename is
     pm-qos-remove-locks-around-blocking-notifier.patch

*** Remember to use Documentation/SubmitChecklist when testing your code ***

See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this

------------------------------------------------------
Subject: pm-qos-remove-locks-around-blocking-notifier
From: mark gross <mgross@xxxxxxxxxxxxxxx>

Remove spin locking around all blocking notifier calls that can sleep.
I had to re-structure some of the code to avoid locking issues.

Signed-off-by: mark gross <mgross@xxxxxxxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxx>
Cc: Venki Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
Cc: Adam Belay <abelay@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 kernel/pm_qos_params.c |   27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff -puN kernel/pm_qos_params.c~pm-qos-remove-locks-around-blocking-notifier kernel/pm_qos_params.c
--- a/kernel/pm_qos_params.c~pm-qos-remove-locks-around-blocking-notifier
+++ a/kernel/pm_qos_params.c
@@ -135,13 +135,14 @@ static s32 min_compare(s32 v1, s32 v2)
 }
 
 
-
-/* assumes pm_qos_lock is held */
 static void update_target(int target)
 {
 	s32 extreme_value;
 	struct requirement_list *node;
+	unsigned long flags;
+	int call_notifier = 0;
 
+	spin_lock_irqsave(&pm_qos_lock, flags);
 	extreme_value = pm_qos_array[target]->default_value;
 	list_for_each_entry(node,
 			&pm_qos_array[target]->requirements.list, list) {
@@ -149,13 +150,16 @@ static void update_target(int target)
 				extreme_value, node->value);
 	}
 	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);
-		blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
-			(unsigned long) pm_qos_array[target]->target_value,
-						NULL);
 	}
+	spin_unlock_irqrestore(&pm_qos_lock, flags);
+
+	if (call_notifier)
+		blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
+			(unsigned long) extreme_value, NULL);
 }
 
 static int register_pm_qos_misc(struct pm_qos_object *qos)
@@ -227,8 +231,8 @@ int pm_qos_add_requirement(int pm_qos_cl
 		spin_lock_irqsave(&pm_qos_lock, flags);
 		list_add(&dep->list,
 			&pm_qos_array[pm_qos_class]->requirements.list);
-		update_target(pm_qos_class);
 		spin_unlock_irqrestore(&pm_qos_lock, flags);
+		update_target(pm_qos_class);
 
 		return 0;
 	}
@@ -269,11 +273,10 @@ int pm_qos_update_requirement(int pm_qos
 			break;
 		}
 	}
+	spin_unlock_irqrestore(&pm_qos_lock, flags);
 	if (pending_update)
 		update_target(pm_qos_class);
 
-	spin_unlock_irqrestore(&pm_qos_lock, flags);
-
 	return 0;
 }
 EXPORT_SYMBOL_GPL(pm_qos_update_requirement);
@@ -303,9 +306,9 @@ void pm_qos_remove_requirement(int pm_qo
 			break;
 		}
 	}
+	spin_unlock_irqrestore(&pm_qos_lock, flags);
 	if (pending_update)
 		update_target(pm_qos_class);
-	spin_unlock_irqrestore(&pm_qos_lock, flags);
 }
 EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);
 
@@ -319,13 +322,10 @@ EXPORT_SYMBOL_GPL(pm_qos_remove_requirem
  */
  int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 {
-	unsigned long flags;
 	int retval;
 
-	spin_lock_irqsave(&pm_qos_lock, flags);
 	retval = blocking_notifier_chain_register(
 			pm_qos_array[pm_qos_class]->notifiers, notifier);
-	spin_unlock_irqrestore(&pm_qos_lock, flags);
 
 	return retval;
 }
@@ -341,13 +341,10 @@ EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
  */
 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 {
-	unsigned long flags;
 	int retval;
 
-	spin_lock_irqsave(&pm_qos_lock, flags);
 	retval = blocking_notifier_chain_unregister(
 			pm_qos_array[pm_qos_class]->notifiers, notifier);
-	spin_unlock_irqrestore(&pm_qos_lock, flags);
 
 	return retval;
 }
_

Patches currently in -mm which might be from mgross@xxxxxxxxxxxxxxx are

pm-qos-infrastructure-and-interface.patch
pm-qos-infrastructure-and-interface-static-initialization-with-blocking-notifiers.patch
pm-qos-remove-locks-around-blocking-notifier.patch
latencyc-use-qos-infrastructure.patch

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