diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c index 3261f142baea..0d5dbed06db4 100644 --- a/drivers/gpu/drm/drm_encoder.c +++ b/drivers/gpu/drm/drm_encoder.c @@ -189,14 +189,26 @@ void drm_encoder_cleanup(struct drm_encoder *encoder) { struct drm_device *dev = encoder->dev; struct drm_bridge *bridge, *next; + LIST_HEAD(tmplist); /* Note that the encoder_list is considered to be static; should we * remove the drm_encoder at runtime we would have to decrement all * the indices on the drm_encoder after us in the encoder_list. */ - list_for_each_entry_safe(bridge, next, &encoder->bridge_chain, - chain_node) + /* + * We need the bridge_chain_mutex to modify the chain, but + * drm_bridge_detach() will call DRM_MODESET_LOCK_ALL_BEGIN() (in + * drm_modeset_lock_fini()), resulting in a possible ABBA circular + * deadlock. Avoid it by first moving all the bridges to a + * temporary list holding the lock, and then calling + * drm_bridge_detach() without the lock. + */ + mutex_lock(&encoder->bridge_chain_mutex); + list_cut_before(&tmplist, &encoder->bridge_chain, &encoder->bridge_chain); + mutex_unlock(&encoder->bridge_chain_mutex); + + list_for_each_entry_safe(bridge, next, &tmplist, chain_node) drm_bridge_detach(bridge); drm_mode_object_unregister(dev, &encoder->base);