lockref: Add lockref_put_not_zero

Put a lockref unless the lockref is dead or its count would become zero. This is the same as lockref_put_or_lock except that the lock is never left held. Signed-off-by: Andreas Gruenbacher <[email protected]> Signed-off-by: Bob Peterson <[email protected]>
pointlessone · Apr 12, 2018 · 450b1f6 · 450b1f6
1 parent e241e3f
commit 450b1f6
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diff --git a/include/linux/lockref.h b/include/linux/lockref.h
@@ -37,6 +37,7 @@ struct lockref {
 extern void lockref_get(struct lockref *);
 extern int lockref_put_return(struct lockref *);
 extern int lockref_get_not_zero(struct lockref *);
+extern int lockref_put_not_zero(struct lockref *);
 extern int lockref_get_or_lock(struct lockref *);
 extern int lockref_put_or_lock(struct lockref *);
 

diff --git a/lib/lockref.c b/lib/lockref.c
@@ -80,6 +80,34 @@ int lockref_get_not_zero(struct lockref *lockref)
 }
 EXPORT_SYMBOL(lockref_get_not_zero);
 
+/**
+ * lockref_put_not_zero - Decrements count unless count <= 1 before decrement
+ * @lockref: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count would become zero
+ */
+int lockref_put_not_zero(struct lockref *lockref)
+{
+	int retval;
+
+	CMPXCHG_LOOP(
+		new.count--;
+		if (old.count <= 1)
+			return 0;
+	,
+		return 1;
+	);
+
+	spin_lock(&lockref->lock);
+	retval = 0;
+	if (lockref->count > 1) {
+		lockref->count--;
+		retval = 1;
+	}
+	spin_unlock(&lockref->lock);
+	return retval;
+}
+EXPORT_SYMBOL(lockref_put_not_zero);
+
 /**
  * lockref_get_or_lock - Increments count unless the count is 0 or dead
  * @lockref: pointer to lockref structure