udev + libbklid: synchronized uevent handling between kernel and ueventd?

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

Hi,

If I understand right, when kernel sends a KOBJ_CHANGE uevent, udevd 
catches it and
update the ctime/mtime of the device file in /dev according to the uevent.
Do I understand the procedure right?

Then a problem occurs to me that, the above procedure is asynchronized,
so sometimes concurreny may happen when kernel send the uevent but udev has
not yet updated the ctime/mtime of device file, making libblkid cache 
still valid and gives wrong result.
(bringing the old thread again: 
http://www.spinics.net/lists/util-linux-ng/msg09154.html)

So i'm wondering is there some synchronized method to send uevent and 
wait for it completed?
Currently I use a method that opens and updates ctime/mtime in kernel 
spaces, but it's somewhat
ugly.
Hope there will be some elegent method.

Thanks,
Qu