Changes in kernel/generic/include/lib/refcount.h [4805495:1a1e124] in mainline

File:

• kernel/generic/include/lib/refcount.h (modified) (2 diffs)

kernel/generic/include/lib/refcount.h

@@ -49 +49 @@
 } atomic_refcount_t;
 
+#define REFCOUNT_INITIALIZER() { \
+        .__cnt = ATOMIC_VAR_INIT(0), \
+}
+
 static inline void refcount_init(atomic_refcount_t *rc)
 {
-        atomic_store_explicit(&rc->__cnt, 0, memory_order_relaxed);
+        atomic_init(&rc->__cnt, 0);
 }
 
@@ -74 +78 @@
         assert(old >= 0);
         (void) old;
+}
+
+/**
+ * Try to upgrade a weak reference.
+ * Naturally, this is contingent on another form of synchronization being used
+ * to ensure that the object continues to exist while the weak reference is in
+ * use.
+ */
+static inline bool refcount_try_up(atomic_refcount_t *rc)
+{
+        int cnt = atomic_load_explicit(&rc->__cnt, memory_order_relaxed);
+
+        while (cnt >= 0) {
+                if (atomic_compare_exchange_weak_explicit(&rc->__cnt, &cnt, cnt + 1,
+                    memory_order_relaxed, memory_order_relaxed)) {
+                        return true;
+                }
+        }
+
+        return false;
 }