[PATCH 2/2] drm/connector: send hotplug uevent on connector cleanup
Ville Syrjälä
ville.syrjala at linux.intel.com
Tue Oct 18 09:24:53 UTC 2022
On Mon, Oct 17, 2022 at 03:32:01PM +0000, Simon Ser wrote:
> A typical DP-MST unplug removes a KMS connector. However care must
> be taken to properly synchronize with user-space. The expected
> sequence of events is the following:
>
> 1. The kernel notices that the DP-MST port is gone.
> 2. The kernel marks the connector as disconnected, then sends a
> uevent to make user-space re-scan the connector list.
> 3. User-space notices the connector goes from connected to disconnected,
> disables it.
> 4. Kernel handles the the IOCTL disabling the connector. On success,
> the very last reference to the struct drm_connector is dropped and
> drm_connector_cleanup() is called.
> 5. The connector is removed from the list, and a uevent is sent to tell
> user-space that the connector disappeared.
>
> The very last step was missing. As a result, user-space thought the
> connector still existed and could try to disable it again. Since the
> kernel no longer knows about the connector, that would end up with
> EINVAL and confused user-space.
So is the uevent sent by the mst delayed destroy work
useless now, or what is going on there?
>
> Fix this by sending a hotplug uevent from drm_connector_cleanup().
>
> Signed-off-by: Simon Ser <contact at emersion.fr>
> Cc: stable at vger.kernel.org
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: Jonas Ådahl <jadahl at redhat.com>
> ---
> drivers/gpu/drm/drm_connector.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index e3142c8142b3..90dad87e9ad0 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -582,6 +582,9 @@ void drm_connector_cleanup(struct drm_connector *connector)
> mutex_destroy(&connector->mutex);
>
> memset(connector, 0, sizeof(*connector));
> +
> + if (dev->registered)
> + drm_sysfs_hotplug_event(dev);
> }
> EXPORT_SYMBOL(drm_connector_cleanup);
>
> --
> 2.38.0
>
--
Ville Syrjälä
Intel
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