1 files changed, 77 insertions, 0 deletions
diff --git a/lib/kref.c b/lib/kref.c
new file mode 100644
index 0000000..9ecd6e8
--- /dev/null
+++ b/lib/kref.c
@@ -0,0 +1,77 @@
+/*
+ * kref.c - library routines for handling generic reference counted objects
+ *
+ * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
+ * Copyright (C) 2004 IBM Corp.
+ *
+ * based on lib/kobject.c which was:
+ * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
+ *
+ * This file is released under the GPLv2.
+ *
+ */
+
+#include <linux/kref.h>
+#include <linux/module.h>
+
+/**
+ * kref_set - initialize object and set refcount to requested number.
+ * @kref: object in question.
+ * @num: initial reference counter
+ */
+void kref_set(struct kref *kref, int num)
+{
+	atomic_set(&kref->refcount, num);
+	smp_mb();
+}
+
+/**
+ * kref_init - initialize object.
+ * @kref: object in question.
+ */
+void kref_init(struct kref *kref)
+{
+	kref_set(kref, 1);
+}
+
+/**
+ * kref_get - increment refcount for object.
+ * @kref: object.
+ */
+void kref_get(struct kref *kref)
+{
+	WARN_ON(!atomic_read(&kref->refcount));
+	atomic_inc(&kref->refcount);
+	smp_mb__after_atomic_inc();
+}
+
+/**
+ * kref_put - decrement refcount for object.
+ * @kref: object.
+ * @release: pointer to the function that will clean up the object when the
+ *	     last reference to the object is released.
+ *	     This pointer is required, and it is not acceptable to pass kfree
+ *	     in as this function.
+ *
+ * Decrement the refcount, and if 0, call release().
+ * Return 1 if the object was removed, otherwise return 0.  Beware, if this
+ * function returns 0, you still can not count on the kref from remaining in
+ * memory.  Only use the return value if you want to see if the kref is now
+ * gone, not present.
+ */
+int kref_put(struct kref *kref, void (*release)(struct kref *kref))
+{
+	WARN_ON(release == NULL);
+	WARN_ON(release == (void (*)(struct kref *))kfree);
+
+	if (atomic_dec_and_test(&kref->refcount)) {
+		release(kref);
+		return 1;
+	}
+	return 0;
+}
+
+EXPORT_SYMBOL(kref_set);
+EXPORT_SYMBOL(kref_init);
+EXPORT_SYMBOL(kref_get);
+EXPORT_SYMBOL(kref_put);