I think there are no direct issues with initialization in the state how it
is now. I suspect it's because "drm_kms_helper_poll_enable()" starts the
first worker thread with a delay, which gives enough time to initialize
required resources. I changed the initialization part to keep it consistent
with the finish part, which is the one causing troubles.

I am not sure where I could move "drm_kms_helper_poll_enable/disable()",
since it is defined in "drm/drm_probe_helper.c", which is only included in
"nouveau_display.c" and "nouveau_connector.c". Both creating a new function
in "nouveau_display.c", and including "probe_helper.h" and using
poll_enable in a different file like "nouveau_fbcon.c" seem like too big
changes for such small fix. I don't know.

Can this new proposed order break something in the finish part as well?
Maybe it would be just better to change the order of "nouveau_drm_finish"
and keep the current order of "noueau_drm_init"?

On Thu, May 5, 2022 at 9:57 PM Lyude Paul <lyude@redhat.com> wrote:

> Hmm, I think we might just need to move the drm_kms_helper_poll_enable()
> call
> to the end here instead of all of nouveau_display_init(). I realized this
> because in nouveau_display_init() it seems that we actually rely on
> nouveau_display_init() to setup hotplug interrupts - which we do actually
> need
> this early on in the driver probe process.
>
> That being said though, drm_kms_helper_poll_enable() shouldn't be required
> for
> MST short HPD IRQs from working so moving that instead should work.
>
> On Wed, 2022-05-04 at 19:18 +0200, Mark Menzynski wrote:
> > Resources needed for output poll workers are destroyed in
> > nouveau_fbcon_fini() before output poll workers are cleared in
> > nouveau_display_fini(). This means there is a time between fbcon_fini
> > and display_fini, where if output poll happens, it crashes.
> >
> > BUG: KASAN: use-after-free in
> > __drm_fb_helper_initial_config_and_unlock.cold+0x1f3/0x291
> > [drm_kms_helper]
> >
> > Cc: Ben Skeggs <bskeggs@redhat.com>
> > Cc: Karol Herbst <kherbst@redhat.com>
> > Cc: Lyude Paul <lyude@redhat.com>
> > Cc: David Airlie <airlied@linux.ie>
> > Cc: Daniel Vetter <daniel@ffwll.ch>
> > Cc: Sumit Semwal <sumit.semwal@linaro.org>
> > Cc: "Christian König" <christian.koenig@amd.com>
> > Cc: dri-devel@lists.freedesktop.org
> > Cc: nouveau@lists.freedesktop.org
> > Cc: linux-kernel@vger.kernel.org
> > Cc: linux-media@vger.kernel.org
> > Cc: linaro-mm-sig@lists.linaro.org
> > Signed-off-by: Mark Menzynski <mmenzyns@redhat.com>
> > ---
> >  drivers/gpu/drm/nouveau/nouveau_drm.c | 17 ++++++++---------
> >  1 file changed, 8 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c
> > b/drivers/gpu/drm/nouveau/nouveau_drm.c
> > index 561309d447e0..773efdd20d2f 100644
> > --- a/drivers/gpu/drm/nouveau/nouveau_drm.c
> > +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
> > @@ -588,12 +588,6 @@ nouveau_drm_device_init(struct drm_device *dev)
> >         if (ret)
> >                 goto fail_dispctor;
> >
> > -       if (dev->mode_config.num_crtc) {
> > -               ret = nouveau_display_init(dev, false, false);
> > -               if (ret)
> > -                       goto fail_dispinit;
> > -       }
> > -
> >         nouveau_debugfs_init(drm);
> >         nouveau_hwmon_init(dev);
> >         nouveau_svm_init(drm);
> > @@ -601,6 +595,12 @@ nouveau_drm_device_init(struct drm_device *dev)
> >         nouveau_fbcon_init(dev);
> >         nouveau_led_init(dev);
> >
> > +       if (dev->mode_config.num_crtc) {
> > +               ret = nouveau_display_init(dev, false, false);
> > +               if (ret)
> > +                       goto fail_dispinit;
> > +       }
> > +
> >         if (nouveau_pmops_runtime()) {
> >                 pm_runtime_use_autosuspend(dev->dev);
> >                 pm_runtime_set_autosuspend_delay(dev->dev, 5000);
> > @@ -641,15 +641,14 @@ nouveau_drm_device_fini(struct drm_device *dev)
> >                 pm_runtime_forbid(dev->dev);
> >         }
> >
> > +       if (dev->mode_config.num_crtc)
> > +               nouveau_display_fini(dev, false, false);
> >         nouveau_led_fini(dev);
> >         nouveau_fbcon_fini(dev);
> >         nouveau_dmem_fini(drm);
> >         nouveau_svm_fini(drm);
> >         nouveau_hwmon_fini(dev);
> >         nouveau_debugfs_fini(drm);
> > -
> > -       if (dev->mode_config.num_crtc)
> > -               nouveau_display_fini(dev, false, false);
> >         nouveau_display_destroy(dev);
> >
> >         nouveau_accel_fini(drm);
>
> --
> Cheers,
>  Lyude Paul (she/her)
>  Software Engineer at Red Hat
>
>