Re: [PATCH 2/2 RESEND] drm/bridge: Add extra checks in pre_enable and post_enable

[AngeloGioacchino Del Regno]

Il 11/03/22 10:34, Ricardo Cañuelo ha scritto:

Depending on the bridge code, certain userspace events during a driver
teardown (such as a DRM ioctl call) might cause a race condition where
the drm_bridge_chain_pre_enable() and drm_bridge_chain_post_enable()
functions could be called for a bridge that has just been detached and
removed from the bridge chain of an encoder.

This change makes these functions a bit more robust by bailing out if
the bridge has already been detached.

Tested on an Acer Chromebook R13 (Elm, MT8173) with Debian Sid.

Signed-off-by: Ricardo Cañuelo 


On various chromebooks with different MediaTek SoC models, and on
Qualcomm SC7180 Trogdor,

Tested-by: AngeloGioacchino Del Regno 

[PATCH 2/2 RESEND] drm/bridge: Add extra checks in pre_enable and post_enable

[Ricardo Cañuelo]

Depending on the bridge code, certain userspace events during a driver
teardown (such as a DRM ioctl call) might cause a race condition where
the drm_bridge_chain_pre_enable() and drm_bridge_chain_post_enable()
functions could be called for a bridge that has just been detached and
removed from the bridge chain of an encoder.

This change makes these functions a bit more robust by bailing out if
the bridge has already been detached.

Tested on an Acer Chromebook R13 (Elm, MT8173) with Debian Sid.

Signed-off-by: Ricardo Cañuelo 
---
 drivers/gpu/drm/drm_bridge.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index c96847fc0ebc..e074aa456dd1 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -529,7 +529,7 @@ void drm_bridge_chain_post_disable(struct drm_bridge 
*bridge)
 {
struct drm_encoder *encoder;
 
-   if (!bridge)
+   if (!bridge || !bridge->dev)
return;
 
encoder = bridge->encoder;
@@ -585,7 +585,7 @@ void drm_bridge_chain_pre_enable(struct drm_bridge *bridge)
struct drm_encoder *encoder;
struct drm_bridge *iter;
 
-   if (!bridge)
+   if (!bridge || !bridge->dev)
return;
 
encoder = bridge->encoder;
-- 
2.25.1