Re: [PATCH] rust: DmaFence: Add better warning through Device reference

[Philipp Stanner <phasta@mailbox.org>]

On Fri, 2026-09-25 at 17:50 +0200, Danilo Krummrich wrote:
> On Fri Sep 25, 2026 at 3:08 PM CEST, Philipp Stanner wrote:
> > The driver can avoid dropping half-forgotten stuff by calling
> > jobqueue.complete_all_jobs(ECANCELED) immediately before dropping,
> > which allows us for having the warning without false-positives.
> 
> This would just move it up a layer from inventing a new type around DriverFence
> to invent a new type around Jobqueue which does that instead.
> 
> But the Jobqueue won't have any procedural teardown, it has to teardown stuff in
> drop() anyway, which includes dropping jobs already.
> 
> What I'm saying is that there's not much value in DriverFence::drop() having
> this warning in the first place, which then either the driver or the jobqueue
> has to work around on teardown.

I guess we agree that it would be a horrible bug if there's still a
command buffer running on the GPU that can access memory which might
have been freed once the associated fence signaled.

So I suppose what you are saying is more: there is not much value in
the case of *JobQueue*, basically because all the jobs live inside of
it anyways.

So I suppose we agree that a warning is fine. It won't fire in JQ
anyways, but might benefit others.


P.