Fix: set BT object's shared flag in all modes

Issue
=====
The bt_object_set_is_shared() function is only effective in a developer
mode build. Since the shared flag is 0 when allocated, and
bt_object_init() calls bt_object_set_is_shared() to make the object
shared initially, all objects are non-shared in non-developer mode.

This was the initial goal, because the only purpose of this shared
flag was to check if the developer is calling bt_get() or bt_put()
with a non-shared object. This check is only performed in developer
mode anyway. However, the object pool system resets the object's
reference count to 1 only when it is shared.

Solution
========
Make bt_object_set_is_shared() always effective, and make the object
pool unconditionally reset the reference count to 1 when recycling. This
avoids a check and the reference count is always 1 for a unique object
anyway (the test was superfluous).

I leave bt_object_set_is_shared() to be always enabled for future use
cases: it does not cost a lot to have it executed in non-developer mode
as its execution cost is amortized anyway for recycled objects.

Known drawbacks
===============
Unnoticeable performance impact.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>

diff --git a/include/babeltrace/object-internal.h b/include/babeltrace/object-internal.h
index 4efba28e8278f8b721c7f06a45794a307dc61ec9..afb9e6eee3cb0cebe2137273bb1fbc637cd43d71 100644 (file)
--- a/include/babeltrace/object-internal.h
+++ b/include/babeltrace/object-internal.h
@@ -50,7 +50,7 @@ struct bt_object {
 
        /*
         * True if this object is shared, that is, it uses reference
-        * counting. Only used in developer mode.
+        * counting.
         */
        bool is_shared;
 };
@@ -137,27 +137,21 @@ void bt_object_set_parent(void *child_ptr, void *parent)
 #endif
 
        /*
-        * It is assumed that a "child" being "parented" is publicly reachable.
-        * Therefore, a reference to its parent must be taken. The reference
-        * to the parent will be released once the object's reference count
-        * falls to zero.
+        * It is assumed that a "child" being "parented" is publicly
+        * reachable. Therefore, a reference to its parent must be
+        * taken. The reference to the parent will be released once the
+        * object's reference count falls to zero.
         */
        BT_PUT(child->parent);
        child->parent = bt_get(parent);
 }
 
-#ifdef BT_DEV_MODE
 static inline
-void _bt_object_set_is_shared(struct bt_object *obj, bool is_shared)
+void bt_object_set_is_shared(struct bt_object *obj, bool is_shared)
 {
        obj->is_shared = is_shared;
 }
 
-# define bt_object_set_is_shared       _bt_object_set_is_shared
-#else
-# define bt_object_set_is_shared(_obj, _is_shared)
-#endif
-
 static inline
 void bt_object_init(void *ptr, bt_object_release_func release)
 {

diff --git a/include/babeltrace/object-pool-internal.h b/include/babeltrace/object-pool-internal.h
index fc9d8c0a0df2f9359e2854cfa318aaaf6c2147fe..ef855890ab943305fddd009c5384cdeef11e7f81 100644 (file)
--- a/include/babeltrace/object-pool-internal.h
+++ b/include/babeltrace/object-pool-internal.h
@@ -119,11 +119,6 @@ void *bt_object_pool_create_object(struct bt_object_pool *pool)
                pool->size--;
                obj = pool->objects->pdata[pool->size];
                pool->objects->pdata[pool->size] = NULL;
-
-               if (obj->is_shared) {
-                       /* Object is shared: reset reference count to 1 */
-                       obj->ref_count.count = 1;
-               }
                goto end;
        }
 
@@ -152,6 +147,8 @@ end:
 static inline
 void bt_object_pool_recycle_object(struct bt_object_pool *pool, void *obj)
 {
+       struct bt_object *bt_obj = obj;
+
        BT_ASSERT(pool);
        BT_ASSERT(obj);
 
@@ -170,6 +167,10 @@ void bt_object_pool_recycle_object(struct bt_object_pool *pool, void *obj)
                g_ptr_array_set_size(pool->objects, pool->size + 1);
        }
 
+       /* Reset reference count to 1 since it could be 0 now */
+       bt_obj->ref_count.count = 1;
+
+       /* Back to the pool */
        pool->objects->pdata[pool->size] = obj;
        pool->size++;