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);

--