Re: [RFC PATCH 0/3] gpu: nova-core: add basic timer subdevice implementation

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Feb 27, 2025 at 11:40:53PM +0100, Danilo Krummrich wrote:
> On Thu, Feb 27, 2025 at 06:00:13PM -0400, Jason Gunthorpe wrote:
> > On Thu, Feb 27, 2025 at 01:25:10PM -0800, Boqun Feng wrote:
> > > 
> > > Most of the cases, it should be naturally achieved, because you already
> > > bind the objects into your module or driver, otherwise they would be
> > > already cancelled and freed. 
> > 
> > I'm getting the feeling you can probably naturally achieve the
> > required destructors, but I think Danillo is concerned that since it
> > isn't *mandatory* it isn't safe/sound.
> 
> Of course you can "naturally" achieve the required destructors, I even explained
> that in [1]. :-)
> 
> And yes, for *device resources* it is unsound if we do not ensure that the
> device resource is actually dropped at device unbind.

Why not do a runtime validation then?

It would be easy to have an atomic counting how many devres objects
are still alive.

Have remove() WARN_ON to the atomic and a dumb sleep loop until it is 0.

Properly written drives never hit it. Buggy drivers will throw a
warning and otherwise function safely.

I'm thinking the standard design pattern is a problem that is too
complex for static analysis to solve.

Jason