[PATCH] drm: Don't race connector registration

[Chris Wilson]

On Thu, Jan 12, 2017 at 05:15:56PM +0100, Daniel Vetter wrote:
> I was under the misconception that the sysfs dev stuff can be fully
> set up, and then registered all in one step with device_add. That's
> true for properties and property groups, but not for parents and child
> devices. Those must be fully registered before you can register a
> child.
> 
> Add a bit of tracking to make sure that asynchronous mst connector
> hotplugging gets this right. For consistency we rely upon the implicit
> barriers of the connector->mutex, which is taken anyway, to ensure
> that at least either the connector or device registration call will
> work out.
> 
> Mildly tested since I can't reliably reproduce this on my mst box
> here.

Hmm, right it should prevent the oops on load. I think we need to
control the async dp-mst better and stop it running until we have the
device registered, and so if we use in the interim, plonk a WARN_ON on
top for -next and try and fix it for realz. (Probably a
drm_dp_mst_mgr_register() hook?)

Acked-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre