On 2019/4/3 0:13, Markus Armbruster wrote:
Igor Mammedov <imamm...@redhat.com> writes:
On Tue, 2 Apr 2019 21:09:39 +0800
Like Xu <like...@linux.intel.com> wrote:
On 2019/4/2 19:27, Markus Armbruster wrote:
Like Xu <like...@linux.intel.com> writes:
This patch makes the remaining dozen or so uses of the global
current_machine outside vl.c use qdev_get_machine() instead,
and then make current_machine local to vl.c instead of global.
Signed-off-by: Like Xu <like...@linux.intel.com>
You effectively replace
current_machine
by
MACHINE(qdev_get_machine())
qdev_get_machine() uses container_get(), which has a side effect: any
path component that doesn't exist already gets created as "container"
object. In case of qdev_get_machine(), that's just "/machine".
Creating "/machine" as "container" is of course wrong. You therefore
must not use qdev_get_machine() before main() creates "/machine". It
does like this:
object_property_add_child(object_get_root(), "machine",
OBJECT(current_machine), &error_abort);
I recently had several cases of code rearrangements explode because the
reordered code called qdev_get_machine() too early. Makes me rather
skeptical about this patch. To be frank, I consider qdev_get_machine()
a trap for the unwary. container_get(), too.
If we decide using it to make current_machine static a good idea anyway,
we need to check the new uses carefully to make sure they can't run
before main() creates "/machine".
maybe we can assert in qdev_get_machine() if machine hasn't been created yet?
with this at least it will be hard to misuse function or catch invalid users.
(but it still might miss some use cases/CLI options which are not tested)
Good idea. When my code created "/machine" as a container, debugging
the resulting crash took me a bit of time. The assertion you propose
would've saved me some.
Good idea and please help review if this assertion in qdev_get_machine()
could help for your code rearrangement:
if (dev == NULL) {
dev = container_get(object_get_root(), "/machine");
}
+ assert(object_dynamic_cast(dev, TYPE_MACHINE) != NULL);
return dev;
