Re: [PATCH v5 3/3] drm: Add Generic USB Display driver

Den 16.02.2021 14.36, skrev Oliver Neukum:

Am Freitag, den 12.02.2021, 18:46 +0100 schrieb Noralf Trønnes:

...

+static void gud_connector_early_unregister(struct drm_connector *connector) +{

•   struct gud_connector *gconn = to_gud_connector(connector);
  

•   backlight_device_unregister(gconn->backlight);
  

•   cancel_work_sync(&gconn->backlight_work);
  

+}

Hi,

this looks like you are creating a race condition where the queued work may operate on an already unregistered backlight.

backlight_device_unregister() sets bd->ops = NULL. This means that userspace can't update brightness anymore, and thus won't call into this driver. After that it should be safe to flush/cancel the workqueue.

Unless I'm missing something here.

Noralf.