This series prevents a race between DRM bridge removal and usage of the
bridge private_obj during DRM_MODESET_LOCK_ALL_BEGIN/END() and other
locking operations.
== Series description
The need for this series emerged during testing of DRM bridge
hot-plugging. Very rarely on hot-unplug the following warning has appeared:
WARNING: CPU: 0 PID: 123 at include/drm/drm_modeset_lock.h:114
drm_atomic_private_obj_fini+0x64/0x80
...
Call trace:
drm_atomic_private_obj_fini+0x64/0x80
drm_bridge_detach+0x38/0x98
This series does not depend on other series.
== Grand plan
This is part of the work to support hotplug of DRM bridges. The grand plan
was discussed in [0].
Here's the work breakdown (➜ marks the current series):
1. … add refcounting to DRM bridges struct drm_bridge,
based on devm_drm_bridge_alloc()
A. ✔ add new alloc API and refcounting (v6.16)
B. ✔ convert all bridge drivers to new API (v6.17)
C. ✔ kunit tests (v6.17)
D. ✔ add get/put to drm_bridge_add/remove() + attach/detach()
and warn on old allocation pattern (v6.17)
E. … add get/put on drm_bridge accessors
1. ✔ drm_bridge_chain_get_first_bridge(), add cleanup action (v6.18)
2. ✔ drm_bridge_get_prev_bridge() (v6.18)
3. ✔ drm_bridge_get_next_bridge() (v6.19)
4. ✔ drm_for_each_bridge_in_chain() (v6.19)
5. ✔ drm_bridge_connector_init (v6.19)
6. … protect encoder bridge chain with a mutex
7. … of_drm_find_bridge
a. ✔ add of_drm_get_bridge() (v7.0),
convert basic direct users (v7.0-v7.1)
b. ✔ convert direct of_drm_get_bridge() users, part 2 (v7.0)
c. ✔ convert direct of_drm_get_bridge() users, part 3 (v7.0)
d. ✔… convert direct of_drm_get_bridge() users, part 4
(some v7.1, some pending)
e. convert bridge-only drm_of_find_panel_or_bridge() users
8. drm_of_find_panel_or_bridge, *_of_get_bridge
9. ✔ enforce drm_bridge_add before drm_bridge_attach (v6.19)
F. ✔ debugfs improvements
1. ✔ add top-level 'bridges' file (v6.16)
2. ✔ show refcount and list lingering bridges (v6.19)
2. ➜ handle gracefully atomic updates during bridge removal
A. ✔ Add drm_bridge_enter/exit() to protect device resources (v7.0)
B. ➜ protect private_obj removal from list
C. ✔ Add drm_bridge_clear_and_put() (v7.1)
3. … DSI host-device driver interaction
4. ✔ removing the need for the "always-disconnected" connector
5. … Migrate i.MX LCDIF driver to bridge-connector
6. DRM bridge hotplug
A. Bridge hotplug management in the DRM core
B. Device tree description
[0]
https://lore.kernel.org/lkml/[email protected]/#t
Signed-off-by: Luca Ceresoli <[email protected]>
---
Changes in v3:
- Rebased on current drm-misc-next (on 7.0-rc3)
- Small commit message clarification
- Link to v2:
https://lore.kernel.org/r/20251021-drm-bridge-atomic-vs-remove-private_obj-v2-1-412a18399...@bootlin.com
Changes in v2:
- Adapted to work on top of "drm/atomic: Add dev pointer to drm_private_obj"
- Removed 'To: [email protected]', invalid address
- Link to v1:
https://lore.kernel.org/r/20251013-drm-bridge-atomic-vs-remove-private_obj-v1-0-1fc2e5810...@bootlin.com
---
Luca Ceresoli (1):
drm/atomic: drm_atomic_private_obj_fini: protect private_obj removal from
list
drivers/gpu/drm/drm_atomic.c | 6 ++++++
1 file changed, 6 insertions(+)
---
base-commit: 7ea0468380216c10b73633b976d33efa8c12d375
change-id: 20251013-drm-bridge-atomic-vs-remove-private_obj-d792805bebdc
Best regards,
--
Luca Ceresoli <[email protected]>
