X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=lib%2Fovs-atomic.h;h=4d43a42a5e6e739c627407492316d3fc5fe98290;hb=ec292d7d81527b29ae948278c796db2da8f5f255;hp=a9ae4aec560f6f9418953a51c62bc95e3f170a3f;hpb=29ab0cf77c2a03e1c5e61f8899c33ad74762a710;p=sliver-openvswitch.git

diff --git a/lib/ovs-atomic.h b/lib/ovs-atomic.h
index a9ae4aec5..4d43a42a5 100644
--- a/lib/ovs-atomic.h
+++ b/lib/ovs-atomic.h
@@ -84,8 +84,8 @@
  * that.
  *
  *
- * Initialization
- * ==============
+ * Life Cycle
+ * ==========
  *
  * To initialize an atomic variable at its point of definition, use
  * ATOMIC_VAR_INIT:
@@ -98,6 +98,15 @@
  * ...
  *     atomic_init(&ai, 123);
  *
+ * C11 does not hav an destruction function for atomic types, but some
+ * implementations of the OVS atomics do need them.  Thus, the following
+ * function is provided for destroying non-static atomic objects (A is any
+ * atomic type):
+ *
+ *     void atomic_destroy(A *object);
+ *
+ *         Destroys 'object'.
+ *
  *
  * Barriers
  * ========
@@ -204,9 +213,31 @@
  * atomic_flag is a typedef for a type with two states, set and clear, that
  * provides atomic test-and-set functionality.
  *
+ *
+ * Life Cycle
+ * ----------
+ *
  * ATOMIC_FLAG_INIT is an initializer for atomic_flag.  The initial state is
  * "clear".
  *
+ * C11 does not have an initialization or destruction function for atomic_flag,
+ * because implementations should not need one (one may simply
+ * atomic_flag_clear() an uninitialized atomic_flag), but some implementations
+ * of the OVS atomics do need them.  Thus, the following two functions are
+ * provided for initializing and destroying non-static atomic_flags:
+ *
+ *     void atomic_flag_init(volatile atomic_flag *object);
+ *
+ *         Initializes 'object'.  The initial state is "clear".
+ *
+ *     void atomic_flag_destroy(volatile atomic_flag *object);
+ *
+ *         Destroys 'object'.
+ *
+ *
+ * Operations
+ * ----------
+ *
  * The following functions are available.
  *
  *     bool atomic_flag_test_and_set(atomic_flag *object)
@@ -249,4 +280,65 @@
     #endif
 #undef IN_OVS_ATOMIC_H
 
+/* Reference count. */
+struct ovs_refcount {
+    atomic_uint count;
+};
+
+/* Initializes 'refcount'.  The reference count is initially 1. */
+static inline void
+ovs_refcount_init(struct ovs_refcount *refcount)
+{
+    atomic_init(&refcount->count, 1);
+}
+
+/* Destroys 'refcount'. */
+static inline void
+ovs_refcount_destroy(struct ovs_refcount *refcount)
+{
+    atomic_destroy(&refcount->count);
+}
+
+/* Increments 'refcount'. */
+static inline void
+ovs_refcount_ref(struct ovs_refcount *refcount)
+{
+    unsigned int old_refcount;
+
+    atomic_add(&refcount->count, 1, &old_refcount);
+    ovs_assert(old_refcount > 0);
+}
+
+/* Decrements 'refcount' and returns the previous reference count.  Often used
+ * in this form:
+ *
+ * if (ovs_refcount_unref(&object->ref_cnt) == 1) {
+ *     // ...uninitialize object...
+ *     free(object);
+ * }
+ */
+static inline unsigned int
+ovs_refcount_unref(struct ovs_refcount *refcount)
+{
+    unsigned int old_refcount;
+
+    atomic_sub(&refcount->count, 1, &old_refcount);
+    ovs_assert(old_refcount > 0);
+    return old_refcount;
+}
+
+/* Reads and returns 'ref_count_''s current reference count.
+ *
+ * Rarely useful. */
+static inline unsigned int
+ovs_refcount_read(const struct ovs_refcount *refcount_)
+{
+    struct ovs_refcount *refcount
+        = CONST_CAST(struct ovs_refcount *, refcount_);
+    unsigned int count;
+
+    atomic_read(&refcount->count, &count);
+    return count;
+}
+
 #endif /* ovs-atomic.h */