Re: [Qemu-devel] [PATCH 2/6] qdev: unref qdev when device_add fails

[Paolo Bonzini <pbonzini@redhat.com>]

Il 10/09/2013 18:21, Stefan Hajnoczi ha scritto:
> qdev_device_add() leaks the created qdev upon failure.  I suspect this
> problem crept in because qdev_free() unparents the qdev but does not
> drop a reference - confusing name.

Right, the name a leftover from pre-refcounting days.

BTW, not dropping a reference is the right thing to do because the
reference is dropped much earlier, typically as soon as qdev_device_add
returns. The QOM object tree then will still provide means to access
devices, until they are unparented.

In this case, however, qdev_device_add's caller does not have a
reference to free; doing that is the responsibility of qdev_device_add,
since it returns NULL.

> Also drop trailing whitespace after curly bracket.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  qdev-monitor.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index 410cdcb..5657cdc 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -512,6 +512,7 @@ DeviceState *qdev_device_add(QemuOpts *opts)
>      }
>      if (qemu_opt_foreach(opts, set_property, qdev, 1) != 0) {
>          qdev_free(qdev);
> +        object_unref(OBJECT(qdev));
>          return NULL;
>      }
>      if (qdev->id) {
> @@ -523,8 +524,9 @@ DeviceState *qdev_device_add(QemuOpts *opts)
>          object_property_add_child(qdev_get_peripheral_anon(), name,
>                                    OBJECT(qdev), NULL);
>          g_free(name);
> -    }        
> +    }
>      if (qdev_init(qdev) < 0) {
> +        object_unref(OBJECT(qdev));
>          qerror_report(QERR_DEVICE_INIT_FAILED, driver);
>          return NULL;
>      }
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>