[PATCH v2 1/9] lib/ref_tracker: add unlocked leak print helper

[Andrzej Hajda <andrzej.hajda@xxxxxxxxx>]

To have reliable detection of leaks, caller must be able to check under the same
lock both: tracked counter and the leaks. dir.lock is natural candidate for such
lock and unlocked print helper can be called with this lock taken.
As a bonus we can reuse this helper in ref_tracker_dir_exit.

Signed-off-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
Reviewed-by: Chris Wilson <chris.p.wilson@xxxxxxxxx>
---
 include/linux/ref_tracker.h |  8 +++++
 lib/ref_tracker.c           | 66 +++++++++++++++++++++----------------
 2 files changed, 46 insertions(+), 28 deletions(-)

diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index 60f3453be23e6..b9c968a716483 100644
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -32,6 +32,9 @@ static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 
 void ref_tracker_dir_exit(struct ref_tracker_dir *dir);
 
+void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
+			   unsigned int display_limit);
+
 void ref_tracker_dir_print(struct ref_tracker_dir *dir,
 			   unsigned int display_limit);
 
@@ -52,6 +55,11 @@ static inline void ref_tracker_dir_exit(struct ref_tracker_dir *dir)
 {
 }
 
+static inline void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
+					   unsigned int display_limit)
+{
+}
+
 static inline void ref_tracker_dir_print(struct ref_tracker_dir *dir,
 					 unsigned int display_limit)
 {
diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index a6789c0c626b0..1b0c6d645d64a 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -14,6 +14,38 @@ struct ref_tracker {
 	depot_stack_handle_t	free_stack_handle;
 };
 
+void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
+			   unsigned int display_limit)
+{
+	struct ref_tracker *tracker;
+	unsigned int i = 0;
+
+	lockdep_assert_held(&dir->lock);
+
+	list_for_each_entry(tracker, &dir->list, head) {
+		if (i < display_limit) {
+			pr_err("leaked reference.\n");
+			if (tracker->alloc_stack_handle)
+				stack_depot_print(tracker->alloc_stack_handle);
+			i++;
+		} else {
+			break;
+		}
+	}
+}
+EXPORT_SYMBOL(__ref_tracker_dir_print);
+
+void ref_tracker_dir_print(struct ref_tracker_dir *dir,
+			   unsigned int display_limit)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&dir->lock, flags);
+	__ref_tracker_dir_print(dir, display_limit);
+	spin_unlock_irqrestore(&dir->lock, flags);
+}
+EXPORT_SYMBOL(ref_tracker_dir_print);
+
 void ref_tracker_dir_exit(struct ref_tracker_dir *dir)
 {
 	struct ref_tracker *tracker, *n;
@@ -26,13 +58,13 @@ void ref_tracker_dir_exit(struct ref_tracker_dir *dir)
 		kfree(tracker);
 		dir->quarantine_avail++;
 	}
-	list_for_each_entry_safe(tracker, n, &dir->list, head) {
-		pr_err("leaked reference.\n");
-		if (tracker->alloc_stack_handle)
-			stack_depot_print(tracker->alloc_stack_handle);
+	if (!list_empty(&dir->list)) {
+		__ref_tracker_dir_print(dir, 16);
 		leak = true;
-		list_del(&tracker->head);
-		kfree(tracker);
+		list_for_each_entry_safe(tracker, n, &dir->list, head) {
+			list_del(&tracker->head);
+			kfree(tracker);
+		}
 	}
 	spin_unlock_irqrestore(&dir->lock, flags);
 	WARN_ON_ONCE(leak);
@@ -40,28 +72,6 @@ void ref_tracker_dir_exit(struct ref_tracker_dir *dir)
 }
 EXPORT_SYMBOL(ref_tracker_dir_exit);
 
-void ref_tracker_dir_print(struct ref_tracker_dir *dir,
-			   unsigned int display_limit)
-{
-	struct ref_tracker *tracker;
-	unsigned long flags;
-	unsigned int i = 0;
-
-	spin_lock_irqsave(&dir->lock, flags);
-	list_for_each_entry(tracker, &dir->list, head) {
-		if (i < display_limit) {
-			pr_err("leaked reference.\n");
-			if (tracker->alloc_stack_handle)
-				stack_depot_print(tracker->alloc_stack_handle);
-			i++;
-		} else {
-			break;
-		}
-	}
-	spin_unlock_irqrestore(&dir->lock, flags);
-}
-EXPORT_SYMBOL(ref_tracker_dir_print);
-
 int ref_tracker_alloc(struct ref_tracker_dir *dir,
 		      struct ref_tracker **trackerp,
 		      gfp_t gfp)
-- 
2.25.1