[PATCH] drm: avoid spurious EBUSY due to nonblocking atomic modesets

[Daniel Stone]

On Tue, 22 Sep 2020 at 15:04, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> On Tue, Sep 22, 2020 at 3:36 PM Marius Vlad <marius.vlad at collabora.com> wrote:
> > Gentle ping. I've tried out Linus's master tree and, and like Pekka,
> > I've noticed this isn't integrated/added.
>
> Defacto the uapi we have now is that userspace needs to ignore "spurious" EBUSY.

This really, really, really, bites.

I think we need a guarantee that this never happens if ALLOW_MODESET
is always used in blocking mode, plus in future a cap we can use to
detect that we won't be getting spurious EBUSY events.

I really don't want to ever paper over this, because it's one of the
clearest indications that userspace has its timing/signalling wrong.

Cheers,
Daniel