Qref is similar to kref. It hides the refcnt detail and provides
a common interface. And this patch is based on the idiom of refcnt,
and adopts some optimization about memory model, which finally
falls back on gcc implementation.
Signed-off-by: Liu Ping Fan <pingf...@linux.vnet.ibm.com>
---
include/qom/object.h | 34 ++++++++++++++++++++++++++++++++++
1 file changed, 34 insertions(+)
diff --git a/include/qom/object.h b/include/qom/object.h
index 23fc048..2e165fb 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -18,6 +18,7 @@
#include <stdint.h>
#include <stdbool.h>
#include "qemu/queue.h"
+#include "qemu/osdep.h"
struct Visitor;
struct Error;
@@ -363,6 +364,10 @@ struct ObjectClass
ObjectUnparent *unparent;
};
+typedef struct Qref {
+ int32_t count;
+} Qref;
+
/**
* Object:
*
@@ -1133,5 +1138,34 @@ int object_child_foreach(Object *obj, int (*fn)(Object
*child, void *opaque),
*/
Object *container_get(Object *root, const char *path);
+static inline void qref_get(Qref *qref)
+{
+#ifdef __ATOMIC_RELAXED
+ __atomic_fetch_add(&qref->count, 1, __ATOMIC_RELAXED);
+#else
+ __sync_fetch_and_add(&qref->count, 1);
+#endif
+}
+
+typedef void (*ReleaseFn)(Qref *);
+static inline void qref_put(Qref *qref, ReleaseFn release)
+{
+ int32_t i;
+
+#ifdef __ATOMIC_RELAXED
+ i = __atomic_fetch_add(&qref->count, -1, __ATOMIC_RELAXED);
+ g_assert(i > 0);
+ if (unlikely(i == 1)) {
+ __atomic_thread_fence(__ATOMIC_SEQ_CST);
+ release(qref);
+ }
+#else
+ i = __sync_fetch_and_add(&qref->count, -1);
+ g_assert(i > 0);
+ if (unlikely(i == 1)) {
+ release(qref);
+ }
+#endif
+}
#endif
--
1.8.1.4
