On Wed, Jan 15, 2020 at 04:36:14PM +0100, Christoph Hellwig wrote:

synchronous and currently hack that up, so a version of the percpu_ref
that actually waits for the other references to away like we hacked
up various places seems to exactly suit your requirements.

Ah, yes, sounds like a similar goal, many cases I'm thinking about
also hack up a kref to trigger a completion to make it
synchronous.

Jason