Re: [PATCH net-next 7/9] devlink: allow registering parameters after the instance

On Thu, Jan 12, 2023 at 11:20:21AM -0800, Jakub Kicinski wrote:

On Thu, 12 Jan 2023 09:07:43 +0200 Leon Romanovsky wrote:

quoted

As a user, I don't want to see any late dynamic object addition which is
not triggered by me explicitly. As it doesn't make any sense to add
various delays per-vendor/kernel in configuration scripts just because
not everything is ready. Users need predictability, lazy addition of
objects adds chaos instead.

Agree with Jakub, it is anti-pattern.

To be clear my preference would be to always construct the three from
the root. Register the main instance, then sub-objects. I mean - you
tried forcing the opposite order and it only succeeded in 90-something
percent of cases. There's always special cases.

I don't understand your concern about user experience here. We have
notifications for each sub-object. Plus I think drivers should hold 
the instance lock throughout the probe routine. I don't see a scenario
in which registering the main instance first would lead to retry/sleep
hacks in user space, do you? I'm talking about devlink and the subobjs
we have specifically.

The term "dynamic object addition" means for me what driver authors will
be able to add objects anytime in lifetime of the driver. I'm pretty sure
that once you allow that, we will see zoo here. Over time, you will get
everything from .probe() to workqueues. The latter caused me to write
about retry/sleep hacks.

If you success to force everyone to add objects in .probe() only, it
will be very close to what I tried to achieve.

Thanks