When aliasing a clock with the qdev_alias_clock() function, a new link
property is created on the device aliasing the clock. The link points
to the aliased clock and use the OBJ_PROP_LINK_STRONG flag. This
property is read only since it does not provide a check callback for
modifications.
The object_property_add_link() documentation stats that with
OBJ_PROP_LINK_STRONG properties, the linked object reference count get
decremented when the property is deleted. But it is _not_ incremented on
creation (object_property_add_link() does not actually know the link).
This commit increments the reference count on the aliased clock to
ensure the aliased clock stays alive during the property lifetime, and
to avoid a double-free memory error when the property gets deleted.
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Luc Michel <luc@lmichel.fr>
---
In principle, that makes sense. But I don't see any users of that API yet.
It would have been nice to have some unit tests for qdev-clock.h..
hw/core/qdev-clock.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/hw/core/qdev-clock.c b/hw/core/qdev-clock.c
index 6a9a340d0f..eb05f2a13c 100644
--- a/hw/core/qdev-clock.c
+++ b/hw/core/qdev-clock.c
@@ -59,10 +59,18 @@ static NamedClockList *qdev_init_clocklist(DeviceState *dev, const char *name,
} else {
object_property_add_link(OBJECT(dev), name,
object_get_typename(OBJECT(clk)),
(Object **) &ncl->clock,
NULL, OBJ_PROP_LINK_STRONG);
+ /*
+ * Since the link property has the OBJ_PROP_LINK_STRONG flag, the clk
+ * object reference count gets decremented on property deletion.
+ * However object_property_add_link does not increment it since it
+ * doesn't know the linked object. Increment it here to ensure the
+ * aliased clock stays alive during this device life-time.
+ */
+ object_ref(OBJECT(clk));
}
ncl->clock = clk;
QLIST_INSERT_HEAD(&dev->clocks, ncl, node);
--
2.28.0