Tofu: initial version

Change-Id: I9c464d5af883c18715a97ca9e9981cf73b260f90

kernel/include/kref.h

@@ -0,0 +1,84 @@
+/*
+ * kref.h - library routines for handling generic reference counted objects
+ * (based on Linux implementation)
+ *
+ * This file is released under the GPLv2.
+ *
+ */
+
+#ifndef _KREF_H_
+#define _KREF_H_
+
+#include <ihk/atomic.h>
+#include <ihk/lock.h>
+
+/*
+ * Bit 30 marks a kref as McKernel internal.
+ * This can be used to distinguish krefs from Linux and
+ * it also ensures that a non deallocated kref will not
+ * crash the Linux allocator.
+ */
+#define MCKERNEL_KREF_MARK	(1U << 30)
+
+struct kref {
+	ihk_atomic_t		refcount;
+};
+
+#define KREF_INIT(n)	{ .refcount = IHK_ATOMIC_INIT(MCKERNEL_KREF_MARK + n), }
+
+/**
+ * kref_init - initialize object.
+ * @kref: object in question.
+ */
+static inline void kref_init(struct kref *kref)
+{
+	ihk_atomic_set(&kref->refcount, MCKERNEL_KREF_MARK + 1);
+}
+
+static inline unsigned int kref_read(const struct kref *kref)
+{
+	return (ihk_atomic_read(&kref->refcount) & ~(MCKERNEL_KREF_MARK));
+}
+
+static inline unsigned int kref_is_mckernel(const struct kref *kref)
+{
+	return (ihk_atomic_read(&kref->refcount) & (MCKERNEL_KREF_MARK));
+}
+
+/**
+ * kref_get - increment refcount for object.
+ * @kref: object.
+ */
+static inline void kref_get(struct kref *kref)
+{
+	ihk_atomic_inc(&kref->refcount);
+}
+
+/**
+ * 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.  If the caller does pass kfree to this
+ *	     function, you will be publicly mocked mercilessly by the kref
+ *	     maintainer, and anyone else who happens to notice it.  You have
+ *	     been warned.
+ *
+ * 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.
+ */
+static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref))
+{
+	//if (ihk_atomic_dec_and_test(&kref->refcount)) {
+	if (ihk_atomic_sub_return(1, &kref->refcount) == MCKERNEL_KREF_MARK) {
+		release(kref);
+		return 1;
+	}
+	return 0;
+}
+
+#endif /* _KREF_H_ */